Abstracts from Society for Neuroscience (SFN), San Diego, California • October 23-27, 2004

45 entries found for : sfn2004

Intraventricular injection of CRF receptor 2 antisense oligonucleotide reduces burn-induced hypermetabolism

Chance WT, Dayal R, Friend L, Sheriff S (2004) Intraventricular injection of CRF receptor 2 antisense oligonucleotide reduces burn-induced hypermetabolism. Neuroscience 2004 Abstracts 890.22. Society for Neuroscience, San Diego, CA.

Summary: Following major burn trauma, mammals exhibit a prolonged hypermetabolic response proportional to the size of the burn. The ability to control metabolic rate would likely result in better clinical management of burn patients. Our research employing a saporin-CRF conjugate to lesion CRF receptors suggested that activity at CRF receptor(R)-2 mediated increased resting energy expenditure (REE) in burned rats. In the present study we assessed whether treatment of burned rats with antisense oligonucleotides (ON) to CRF or CRF R-2 would reduce REE. Following anesthetization (ketamine/xylazine:80/15 mg/kg,), cannulae (24 ga) were implanted into the 3rd ventricle of 52 adult, male, SD rats. Two weeks later, these rats were anesthetized and subjected to a 25 sec, 30% body surface area, open flame burn (n = 30) or sham burn procedures (n = 22). Following (2-6 days) the burn trauma, either sense or antisense ONs to CRF (15 ug) or CRF R-2 (20 ug) was injected, ivt. REE (kcal/kg/24 hrs) was determined in these rats 7 and 14 days after burn by indirect calorimetry. Treatment with CRF antisense ON did not reduce REE in any groups. Burned rats given the CRF R-2 sense ON exhibited significant hypermetabolism both 7 (188±5 vs 156± 9) and 14 (201±8 vs 151±14) days post-burn, as compared to sham-burned rats. Burned rats treated with the CRF R-2 antisense ON were not significantly different from sham burned rats 7 (169±8) or 14 (167±5) days post-burn. Since the antisense treatment should decrease translation of message into protein at the receptor, these results suggest that activity at the CRF-2 receptor is necessary for expression of burn-induced hypermetabolism. Therefore, it is possible that CRF-2 receptor antagonists could be useful in treating burn-induced hypermetabolism.

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PVN anti-SERT-SAP injections reduce body weight gain, normal and glucoprivic feeding, and hypoglycemia- and stress-induced corticosterone responses

Zhou D, Levin BE (2004) PVN anti-SERT-SAP injections reduce body weight gain, normal and glucoprivic feeding, and hypoglycemia- and stress-induced corticosterone responses. Neuroscience 2004 Abstracts 893.14. Society for Neuroscience, San Diego, CA.

Summary: Hindbrain serotonin (5HT) neurons are highly ramified with single neurons innervating several forebrain and hypothalamic areas such as the paraventricular nucleus (PVN). To assess their importance in the regulation of energy homeostasis and hypothalamo-pituitary-adrenal activation, anti-SERT-SAP (SS), an antibody to the 5HT re-uptake transporter (SERT) conjugated to a ribosomal toxin saporin (SAP), was injected bilaterally into the PVN of rats to selectively destroy hypothalamically-projecting 5HT neurons. Unconjugated SAP injections served as controls. SS injections significantly destroyed rostral dorsal (DRa) and medial raphe (MRa) 5HT neurons. Compared to SAP rats, SS rats had 13% lower food intake (SAP 71.2+3.2g vs. SS 61.7+2.8g, P=0.037) and 44% lower body weight gain (SAP 26.9+2.9g vs. SS 15.3+.31g, P=0.003) over 8d. Food intake over 24h (but not 3h) after insulin-induced hypoglycemia was 22% lower in SS (25.1±1.2g) than SAP rats (32.2±0.9g, P<0.01) and their blood glucose levels dropped more during 120min of hypoglycemia (AUC, -3945+77mg/dl) than SAP controls (-3675+108; P=0.01) suggesting a counterregulatory defect. This was supported by a 39% lower 30min corticosterone (Cort) response to hypoglycemia in SS (126±25µg/ml) vs. SAP controls (208±21 μg/ml, P<0.05). On the other hand, the glucagon response to hypoglycemia did not differ between SS (81.3±10.1pg/ml) and SAP-injected rats (65.8±7.6pg/ml; P=0.72). Finally, SS injections reduced the Cort response to 30min immobilization stress (SS 389±21 vs. SAP 460±25 µg/mg; P<0.05) by 15% without significantly affecting basal levels (SS 18.0±3.9 vs. SAP 10.1±2.2 µg/ml, P=0.09). Thus, DRa and MRa 5HT projections to the forebrain play a significant role in energy homeostasis, hypoglycemia-induced feeding and the Cort responses to both hypoglycemia and stress.

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Injection of the targeted-toxin, neuropeptide Y-saporin (NPY-SAP), into the basomedial hypothalamus (BMH) disrupts leptin and ghrelin signaling

Bugarith KH, Li A, Dinh TT, Ritter S (2004) Injection of the targeted-toxin, neuropeptide Y-saporin (NPY-SAP), into the basomedial hypothalamus (BMH) disrupts leptin and ghrelin signaling. Neuroscience 2004 Abstracts 893.17. Society for Neuroscience, San Diego, CA.

Summary: NPY-SAP, a conjugate of the peptide NPY and saporin, a ribosomal inactivating toxin, specifically lesions NPY receptor-expressing cells. We injected NPY-SAP into the BMH and examined the effects of various inhibitory (leptin, 5ug/5ul/day, icv; GLP-1, 5ug/5ul, icv, CCK, 4ug/kg, ip;) and stimulatory (ghrelin, 2ug/5ul, icv; NPY, 500ng/100nl, icv; 2-DG, 100, 200 and 400 mg/kg; MA, 68mg/kg, ip) peptide and metabolic signals that influence food intake. We also examined the effect of NPY-SAP on NPY, CART and AGRP mRNA expression in NPY/AGRP and POMC/CART neurons known to express the NPY receptor, and the effect of NPY and NPY Y1 receptor immunoreactivity in the arcuate (Arc) nucleus. We found that the anorectic effects of leptin and the orexigenic effects of ghrelin were abolished by NPY-SAP. The stimulation of feeding induced by NPY, 2-DG and MA, and the suppression of deprivation-induced feeding by GLP-1 and CCK were not attenuated by NPY-SAP injection. There was a profound but localized reduction of NPY Y1 receptor-, and NPY fiber and terminal immunoreactivity, and NPY, AGRP and CART mRNA expression in the Arc. NPY-SAP did not appear to be retrogradely transported in hindbrain NPY neurons with hypothalamic terminals. Leptin and ghrelin are thought to act primarily on Arc NPY/AGRP and POMC/CART neurons to mediate their ingestive effects, whereas the effects of 2-DG, MA, CCK and GLP-1 are thought to be mediated in part by mechanisms outside the Arc. Present results show that BMH injections of NPY-SAP selectively impair controls mediated by Arc neural circuitry without causing widespread disruption of other ingestive behaviors. Results also reveal important ingestive controls that do not require Arc NPY/AGRP and POMC/CART neurons.

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Local striatal deletions of neurokinin-1 receptor-expressing neurons protect against methamphetamine-induced neural damage

Xu W, Zhu JPQ, Angulo JA (2004) Local striatal deletions of neurokinin-1 receptor-expressing neurons protect against methamphetamine-induced neural damage. Neuroscience 2004 Abstracts 908.8. Society for Neuroscience, San Diego, CA.

Summary: Recent collective evidence from our laboratory and others has implicated the peptidergic system involving the neuropeptide substance P (SP) and its receptor, neurokinin-1 (NK-1), in mediating METH-induced adverse effects in the neostriatum. Here we test to see if local striatal abolishment of the NK-1 receptor-signaling pathway can protect from METH-induced neural damage in the striatum. Selective striatal knockouts of this pathway was done using an intrastriatal injection of [Sar9,Met(O2)11]substance P conjugated to the ribosomal-inactivating cytotoxin saporin (SSP-SAP). Selective striatal elimination of NK-1 receptor-expressing neurons demonstrated protection against METH-induced apoptosis by TUNEL-labeling. This further confirms the important modulatory effects of this peptidergic receptor in striatum.

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Modulation of late long-term potentiation in the hippocampus: Effect of cholinergic and GABAergic medial septal lesions

Montoya DA, Pang K (2004) Modulation of late long-term potentiation in the hippocampus: Effect of cholinergic and GABAergic medial septal lesions. Neuroscience 2004 Abstracts 972.12. Society for Neuroscience, San Diego, CA.

Summary: Long Term Potentiation (LTP) is an endurable change in synaptic efficacy produced by brief repetitive stimulation of specific afferents and is a cellular model of long term memory. The duration of LTP can vary depending on the intensity fo the inducing tetanic stimulation, which reflects the different phases of LTP. Early phase LTP does not require protein synthesis, whereas late-phase LTP is dependent on protein synthesis. Modulating transmitter systems may also be important in the conversion of early-phase to late-phase LTP. In previous studies, stimulation of the medial septum (MS) converted an early-phase LTP to a late-phase LTP in the dentate gyrus. These results suggest that cholinergic or GABA septohippocampal neurons may be important in late-phase LTP. The present study will evaluate whether cholinergic or GABAergic septohippocampal neurons are important in the development of long-lasting LTP after MS stimulation. LTP will be assessed in urethane anesthetized rats with prior intraseptal saline, 192 IgG-saporin (SAP; 0.245 micrograms/microliter) or kainic acid KA; 0.5 microgram/microliter) treatment. 192 IgG-saporin selectively destroys cholinergic MS neurons, while kainic acid preferentially damages GABAergic septohippocampal neurons. In preliminary studies, 5 trains of perforant path stimulation (15 pulses at 400 Hz/train) produced a transient LTP of the dentate population spike in urethane anesthetized rats. In this preparation, LTP lasted for about 90 minutes. In future experiments, we will assess whether late-phase LTP develops in the urethane anesthetized rats with MS stimulation followed by perforant path stimulation trains. If this occurs, rats with cholinergic or GABAergic MS lesions will be evaluated.

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Effect of removal of neurons expressing serotonin reuptake transporter on male sexual reflexes

Gravitt KC, Cai RS, Marson L (2004) Effect of removal of neurons expressing serotonin reuptake transporter on male sexual reflexes. Neuroscience 2004 Abstracts 998.2. Society for Neuroscience, San Diego, CA.

Summary: Ejaculatory reflexes are regulated by spinal circuits that are tonically inhibited or facilitated by specific regions of the brain. Serotonin can facilitate or inhibit sexual responses depending on the site of action and the predominate receptor subtype involved. Sexual function, in particular ejaculation, can be reduced by administration of serotonin reuptake inhibitors (SSRI’s). The urethrogenital (UG) reflex comprises erections, rhythmic contractions of perineal muscles and ejaculation in male rats. We previously demonstrated that a direct pathway from the nucleus paragigantocellularis to the lumbosacral cord is involved in regulating the tonic inhibition of UG reflexes. Neurons in the ventral medulla contain serotonin and removal of serotonin inputs in the spinal cord allow the UG reflex to be exposed. The present study examined the effect of specific lesions of ventral medullary neurons containing the serotonin reuptake transporter (SERT) on sexual reflexes. Anti-SERT-saporin (50-100nl, 1uM) was injected bilaterally into the nPGi of male rats. Ten-fourteen days following surgery, animals were deeply anesthetized and the presence of the UG reflex examined. Urethral stimulation was performed before and after cutting the spinal cord (SCT) and recordings made from the bulbospongiosus muscle. Following the experiment immunocytochemical localization of serotonin was examined. In control rats the UG reflex was not present before SCT. In 50% of males that received anti-SERT-saporin the UG reflex was exposed before SCT. Responses after spinal cord transection were similar in all groups. Rats treated with ant-SERT-saporin showed a significant reduction in the number of serotonin containing neurons and a decrease in the intensity staining in the nPGi, parapyramidal region and medullary raphe. These studies suggest that neurons containing serotonin reuptake transporter systems are involved inhibiting male sexual reflexes.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Septohippocampal cholinergic lesion and hippocampal alpha-secretase activity in rat

Pokala VN, Fitz NF, Witt-Enderby PA, Johnson DA (2004) Septohippocampal cholinergic lesion and hippocampal alpha-secretase activity in rat. Neuroscience 2004 Abstracts 846.14. Society for Neuroscience, San Diego, CA.

Summary: Previously we have shown that selective cholinergic lesion of the septohippocampal pathway in the rat resulted in a significant decrease in hippocampal extracellular acetylcholine (ACh) concentration, a compensatory increase in muscarinic receptor binding, but a decrease in muscarinic receptor-coupled G protein activation. The intent of this study was to investigate the effect of selective cholinergic lesion of the septohippocampal pathway on hippocampal alpha-secretase activity and expression. Alpha-secretase is an enzyme responsible for the proteolytic cleavage of amyloid protein precursor (APP) to release a neuroprotective soluble amyloid protein precursor (sAPP). Sprague-Dawley rats were infused into the medial septum with either the selective cholinergic immunotoxin 192 IgG-saporin (0.22 mg in 1ml aCSF) or vehicle. After 6 weeks the rats were euthanized and the hippocampus dissected from the brain and quickly frozen. Hippocampal homogenate was analyzed for alpha-secretase activity and expression. The results demonstrated an 80% decrease in alpha-secretase activity in SAP treated animals compared to control.

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IB4-SAP reduces IB4 staining in the spinal cord and prevents axotomy induced sprouting of Aβ fibers

Pearson MS, Woods M, Whiteside GT, Garrison AE, Pomonis JD, Walker K (2004) IB4-SAP reduces IB4 staining in the spinal cord and prevents axotomy induced sprouting of Aβ fibers. Neuroscience 2004 Abstracts 858.6. Society for Neuroscience, San Diego, CA.

Summary: Peripheral nerve injury results in hyperalgesia and allodynia. It has been proposed that sprouting of myelinated touch responsive Aß-fibers into the innervation territory of pain sensitive C-fibers in the spinal cord contributes to these abnormal behaviors. The extent of sprouting has recently been challenged and it has been proposed that C-fibers rather than Aß-fibers are involved. We have investigated whether selectively ablating a population of small diameter nociceptors using isolectin B4 conjugated to saporin (IB4-SAP), reduces axotomy-induced sprouting. Male Sprague-Dawley rats received intraneural injections of either IB4-SAP or PBS (3 µl, 0.66 µg/µl) and two weeks later the sciatic nerve was axotomized at the mid-thigh level. Two weeks later, the sciatic nerve was injected with the retrograde tracer, cholera toxin-ß subunit (CTB) (2 µl, 2%) that selectively traces Aß-fibers. Three days post CTB the animals were perfused, the spinal cord harvested, sectioned and stained immunohistochemically for IB4 and CTB. IB4-SAP treatment resulted in a substantial reduction of IB4 staining in the spinal cord versus PBS injected controls. As previously described, axotomy resulted in considerable CTB immunostaining in laminae I, II and III compared to non-axotomized controls in which it was present only in laminae I and III. IB4-SAP treatment followed by axotomy resulted in a substantial reduction of CTB immunostaining in lamina II compared to PBS injected controls. These results suggest that intraneural IB4-SAP ablates a population of small diameter nociceptors and that axotomy induced CTB staining in lamina II is due to uptake of CTB by C-fibers.

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Immunotoxic destruction of hindbrain catecholamine neurons impairs the vasopressin response to hypovolemia

Ritter S, Flynn FW, Dinh TT (2004) Immunotoxic destruction of hindbrain catecholamine neurons impairs the vasopressin response to hypovolemia. Neuroscience 2004 Abstracts 660.4. Society for Neuroscience, San Diego, CA.

Summary: In order to better understand the involvement of hindbrain catecholamine neurons in hypovolemia-induced vasopressin secretion, we lesioned these neurons selectively using anti-dopamine beta-hydroxylase (dbh) conjugated to the ribosomal toxin, saporin (DSAP). When injected into catecholamine terminal sites, this neurotoxin is selectively internalized by and retrogradely transported in dbh-containing neurons, destroying cell bodies that innervate the injection site. We microinjected DSAP or unconjugated saporin (SAP) control bilaterally into the medial hypothalamus of female rats to destroy catecholamine neurons innervating the magnocellular areas of the paraventricular nucleus (PVH). The lesion was verified at the conclusion of the experiment by analysis of dbh-immunoreactive terminals in the PVH and cell bodies in hindbrain catecholamine cell groups. Two weeks after DSAP injection, hypovolemia was induced by remote withdrawal of blood (1 ml/min for 4.5 min) using a chronically implanted intra-atrial catheter. Blood was sampled between 0-2 and 2-4.5 min and at 20 and 50 min after the start of blood withdrawal. Plasma vasopressin was extracted and analyzed using ELISA. The DSAP lesion severely impaired the vasopressin response. Responses at 20 min were 35 pg/ml in the SAP control and 21 pg/ml in the DSAP rats. Responses at 50 min were 45 pg/ml in the SAP and 23 pg/ml in the DSAP lesioned rats. Results indicate that hindbrain catecholamine neurons play a crucial role in full expression of the vasopressin response to hypovolemia.

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Apnea induced by stimulation of bronchopulmonary C-fibers (PCFs) depends on neurons expressing the neurokinin a receptor (NK1R) in the commissural subnucleus of the nucleus tractus solitarius (cNTS).

Xu F, Zhuang J, Hernandez J, Shi S (2004) Apnea induced by stimulation of bronchopulmonary C-fibers (PCFs) depends on neurons expressing the neurokinin a receptor (NK1R) in the commissural subnucleus of the nucleus tractus solitarius (cNTS). Neuroscience 2004 Abstracts 661.13. Society for Neuroscience, San Diego, CA.

Summary: Stimulation of PCFs by right atrial injection of capsaicin (CAP) reflexly produces an apnea and hypotension via stimulating cNTS neurons. Recent evidence indicates that activation of NK1R within the cNTS significantly amplifies this apneic response (Mutoh, et al., Am J Physiol, 2000). We asked whether the cNTS contained the highest density of the neurons responding to PCF stimulation and expressing NK1R, and what the effect of selective destruction of these neurons was on the cardiorespiratory responses to CAP. In the first series of our experiments, double labeling (c-fos and NK1R immunoreactivity) was used to mark the medullary neurons that were activated by right atrial injection of CAP (0.5-1.0 µg) and displayed NK1R. We found that compared to control (vehicle injection), the greatest enhancement of and highest density of Fos expression were observed within the cNTS, and a number of Fos-stained cNTS neurons had expression of NK1R. In the second series of our experiments, bilateral microinjection (100 nl) of substance P-saporin conjugate (SP-SAP) to selectively destroy the local neurons containing NK1R and SAP (control) into the cNTS was performed in two groups of rats, respectively. Our results showed that at 18 days after SP-SAP (rather than SAP) injection, the majority of cNTS NK1R neurons were destroyed. This lesion did not significantly change cardiorespiratory baseline variables, but did eliminate the apnea and reduce the hypotension induced by CAP. In sharp contrast, the lesion failed to affect the cardiorespiratory responses to hypoxia (10% O2 for 1 min). These findings strongly suggest that cNTS neurons with NK1R are necessary for the PCF-mediated cardiorespiratory responses but are not significantly involved in the cardiorespiratory response to acute hypoxia.

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The basal forebrain cholinergic system is essential for cortical plasticity and functional recovery following brain injury

Conner JM, Chiba AA, Tuszynski MH (2004) The basal forebrain cholinergic system is essential for cortical plasticity and functional recovery following brain injury. Neuroscience 2004 Abstracts 685.12. Society for Neuroscience, San Diego, CA.

Summary: Localized damage to the motor cortex typically results in impaired motor function. Functional recovery following focal brain injury presumably requires the reorganization of cortical circuitry, enabling undamaged areas remote from the lesion site to take over function. Neuronal mechanisms mediating plasticity of cortical representations are not fully understood, but recent studies have indicated that the basal forebrain cholinergic system may play an essential role. In the present study, we investigated the hypothesis that the basal forebrain cholinergic system is essential for enabling cortical reorganization required for functional recovery following focal motor cortex lesions. Following focal cortical injury, performance in a previously learned skilled reaching task dropped by ~75%. After 5-weeks of rehabilitative training, normal (cholinergically-intact) rats recovered 55.2 ± 4.4% of their pre-lesion reaching performance. Rats with specific lesions of the cholinergic neurons projecting to the cortex showed only 18.1 ± 7.7% recovery (p<0.002). Intracortical mapping revealed that massive reorganization of motor representations had occurred in the cortex following focal cortical injury and rehabilitative training. A significant 48.6 ± 12.2% increase (p=0.001) in the size of the rostral forelimb area (RFA) was seen in cholinergically-intact, functionally recovered, rats. In contrast, the size of the RFA did not change in cholinergic-lesioned animals. Subsequent ablation of the RFA completely disrupted skilled reaching performance, suggesting the RFA was essential to the recovered function. These results demonstrate that functional recovery following discrete cortical injury requires basal forebrain cholinergic mechanisms and suggest that the basis for this recovery is the cholinergic-dependent reorganization of motor representations.

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Cell-body lesions of basal forebrain impair reversal learning but not attentional set-shifting in rats

Tait DS, Brown VJ (2004) Cell-body lesions of basal forebrain impair reversal learning but not attentional set-shifting in rats. Neuroscience 2004 Abstracts 779.12. Society for Neuroscience, San Diego, CA.

Summary: There is considerable evidence for a role of basal forebrain acetylcholine in a wide range of attentional tasks (see Sarter & Bruno, 2000, Neurosci, 95:933-952), but previous work from this laboratory found that basal forebrain cholinergic projections are not critical for the acquisition, maintenance and shifting of attentional set (Tait et al, 2002 SfN abstr 286.2). As GABAergic basal forebrain projections to cortex may be important for “cognitive flexibility” (Sarter & Bruno, 2002, Eur J Nsci, 15:1867-1873), the present study assessed the effects of non-specific basal forebrain lesions. Male Lister hooded rats received infusions of 200nl 0.06M ibotenic acid into basal forebrain, at coordinates: nosebar –3.3; AP –0.9; ML ±2.9; DV –6.9. We used the rat attentional-set shifting task (Birrell & Brown, 2000, JNsci, 20:4320-4324), in which rats forage in digging bowls for food rewards, to assess discrimination learning (based on the odor of the bowls or the medium in which the food was hidden), reversal learning and attentional-set shifting (when the relevant aspect of the stimulus is switched; for example, a rat previously attending to odor, now must attend to digging medium or vice versa). There was no impairment in discrimination acquisition or in shifting of attentional-set. Lesioned rats were impaired only on the first of three discrimination reversals, taking significantly longer to reach criterion than controls. Prior evidence indicating no effect of selective BF cholinergic depletion via 192-IgG-saporin administration on reversal performance (Tait et al, 2002) leads us to conclude that the non-cholinergic neurons – most likely the GABAergic projection to prefrontal cortex and thalamus – have an important role in reversal learning. These data are strikingly similar to the effects of excitotoxic basal forebrain lesions in monkeys (Roberts et al, 1992, NSci, 472:251-264).

Related Products: 192-IgG-SAP (Cat. #IT-01)

Attention, uncertainty, and acetylcholine: Effects of nucleus basalis cholinergic lesions on probabilistic inference

Cordova CA, Yu AJ, Chiba AA (2004) Attention, uncertainty, and acetylcholine: Effects of nucleus basalis cholinergic lesions on probabilistic inference. Neuroscience 2004 Abstracts 779.13. Society for Neuroscience, San Diego, CA.

Summary: Animal investigations suggest that the basal forebrain corticopetal cholinergic system helps to regulate attention to unpredictable events. In light of these findings, computational theorists propose that cholinergic neurons precisely alter the way that sensory stimuli are processed in the cortex in light of how well predicted they are. In an initial test of this theory, two groups of rats were trained to respond to probabilistic stimuli presented serially in one of four spatial locations with varying degrees of predictive uncertainty (arising from a 2-layer Hidden Markov model). Following training, one group of rats was given a selective cholinergic lesion of the nucleus basalis/substantia innominata region of the basal forebrain using 192-IgG Saporin. The lesioned rats were unable to allocate attention appropriately, as evidenced by the decreased accuracy of responses to less probable stimuli. These findings provide support for the notion that the basal forebrain corticoptetal cholinergic system facilitates attention by regulating the balance of learned expectations and sensory processing during stimulus inference.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Behavioral characteristics of pedunculopontine tegmental nucleus lesioned and nucleus basalis magnocellularis lesioned rats in a test of vigilance

Taylor CL, Rostron PR, Latimer MP, Winn P (2004) Behavioral characteristics of pedunculopontine tegmental nucleus lesioned and nucleus basalis magnocellularis lesioned rats in a test of vigilance. Neuroscience 2004 Abstracts 780.4. Society for Neuroscience, San Diego, CA.

Summary: Previous work has shown pedunculopontine tegmental nucleus (PPTg) lesioned rats make more omissions on a vigilance task but improve if the target is longer. We compared vigilance performance of PPTg rats with rats bearing 192 IgG Saporin lesions of the nucleus basalis magnocellularis (NbM). The task involved a period of darkness before a dim light of variable duration, followed by a bright light target. A lever press was required during the target to receive food reward, while failure to press during the target constituted an omission. Rats were pre-trained to a criterion of >70% correct and <20% omissions at 1500ms target duration. Post-lesion, rats were assessed for 10 days at 1500ms, 5 days at 4000ms, and 5 further days at 1500ms target durations. Results showed both groups increased omissions relative to controls but this effect was transient in NbM rats. The percentage of omissions in all groups was sensitive to manipulation of target duration. Because increasing target duration also increased the time allowed to make a correct response we re-coded omissions in the 1500ms task to include only those occurring a further 2500ms following target offset (making the response time frame comparable with the 4000ms task). Again, comparison with omissions from the 4000ms task continued to show target duration sensitivity. This finding lends support to PPTg as well as NbM involvement in attention. In order to address why lesioned rats made more omissions in the task we analyzed video data of behaviour at the time of the dim and bright light. Results suggest increased distraction in PPTg lesioned rats while NbM lesioned rats additionally showed failed attempts to lever press in response to the bright signal. This finding has implications for studies using short response time frames where NbM rats may not have time to recover from a failed lever press attempt.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Neurokinin 1 receptor expressing interneurons of the BLA regulate anxiety-like responses in the rat

Truitt WA, Dietrich AD, Fitz SD, Minick PE, Shekhar A (2004) Neurokinin 1 receptor expressing interneurons of the BLA regulate anxiety-like responses in the rat. Neuroscience 2004 Abstracts 782.5. Society for Neuroscience, San Diego, CA.

Summary: The Basolateral Nucleus of the Amygdala (BLA) has been implicated in the regulation and development of anxiety. In general, regarding BLA projection neurons, excitation tends to increase, while inhibition tends to reduce anxiety-like responses. These projection neurons, which comprise approximately 85% of the BLA neurons, are tightly regulated by the activity of local circuit GABAergic interneurons. To date, at least four distinct interneuronal subpopulations have been identified in the BLA, with characteristic morphological and physiological properties suggestive of functional diversity. Yet the in vivo functional selectivity of these subpopulations has not been critically examined. Here we propose to examine the function of one specific interneuronal subpopulation within the BLA by making selective lesions and monitoring anxiety-like behavior. To accomplish this objective the subpopulation of BLA interneurons expressing NK-1r receptors were ablated with the targeted toxin SSP-saporin (SAP). Lesions were made by a series of 6 bilateral, 500nl injections spread throughout the anterior BLA. Control rats were injected with an equal volume of blank-SAP, which does not enter the cells. SSP-SAP injections significantly reduced the number of NK-1r expressing cells compared to blank-SAP treated rats, with little to no nonspecific damage. Lesioning NK-1r expressing cells resulted in increased anxiety-like responses in the social interaction (SI) and elevated plus maze (EPM) tests. Specifically, SI time compared to pre-surgery value was significantly reduced in lesion rats. Lesion rats also had fewer open arm entries in the EPM compared to control rats. Furthermore, lesioned rats failed to recover from this decrease in SI even after 4 weeks of testing. These results suggest that the subpopulation of interneurons within the BLA that express NK-1r is critical in regulating anxiety-like behavior.

Related Products: SSP-SAP (Cat. #IT-11)

Noradrenergic inputs to the bed nucleus of the stria terminalis (BNST) contribute to yohimbine-induced activation of BNST neurons and hypothalamic CRH neurons in rats

Banihashemi L, Rinaman L (2004) Noradrenergic inputs to the bed nucleus of the stria terminalis (BNST) contribute to yohimbine-induced activation of BNST neurons and hypothalamic CRH neurons in rats. Neuroscience 2004 Abstracts 426.10. Society for Neuroscience, San Diego, CA.

Summary: Noradrenergic (NA) inputs to the BNST and hypothalamus are implicated in behavioral and endocrine responses to stress and anxiety. Yohimbine (YO) increases transmitter release from NA terminals, which promotes anxiety and activates CRH neurons at the central apex of the HPA axis. We hypothesized that these effects require NA signaling within the BNST. To test this, saporin toxin conjugated to an antibody against dopamine beta hydroxylase (DSAP; 50-100 nl) was microinjected bilaterally into the BNST to eliminate its NA inputs in adult male Sprague-Dawley rats. After 2 weeks, DSAP-treated rats and intact control rats were injected with YO (0 or 5 mg/kg, i.p) and perfused with fixative 90 min later. Brain sections were processed to reveal DSAP lesion extent and YO-induced cFos activation. DSAP rats displayed nearly complete loss of NA terminals in the BNST, accompanied by moderate loss of hypothalamic NA terminals. Significantly fewer BNST neurons and hypothalamic CRH neurons were activated in DSAP rats after YO compared to activation in intact control rats, whereas parabrachial and central amygdala activation in DSAP rats was not diminished. We conclude that medullary NA neurons projecting to the lateral BNST collateralize to innervate the paraventricular hypothalamus, and that these NA projection neurons are necessary for YO to activate BNST and hypothalamic CRH neurons. Studies are ongoing to determine whether BNST-projecting NA neurons are necessary for YO to inhibit food intake or support conditioned flavor avoidance.

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A novel mouse model for Parkinson’s disease using an immunotoxin directed at the dopamine transporter

Stead S, Doering LC (2004) A novel mouse model for Parkinson’s disease using an immunotoxin directed at the dopamine transporter. Neuroscience 2004 Abstracts 563.1. Society for Neuroscience, San Diego, CA.

Summary: Current laboratory models of Parkinson’s disease utilize neurotoxins directed at midbrain dopamine neurons to mimic nigro-striatal dopaminergic neuron degeneration. To date, however, there is no single model that accurately simulates the pathogenic, histological, biochemical and clinical features relevant for the investigation of PD. The most common laboratory rodent model of Parkinson’s uses the neurotoxin 6-hydroxydopamine (6-OHDA) to cause relatively acute degeneration of the dopamine neurons in the substantia nigra (Schwarting RKW and Huston JP, 1996, Prog Neurobiol., 50:275-331). Axonally transported toxins can be used to make selective lesions in the central nervous system. We have found that a slower degeneration of the SN can be achieved with an immunotoxin directed against the dopamine transporter (DAT). This immunotoxin, consisting of the highly active ribosome inactivating protein Saporin linked to an antibody to the dopamine transporter, was recently reported to cause selective degeneration of the SN in rats (Wiley RG et al., 2003, Cell Mol Neurobiol., 23:839-850.). We have shown that unilateral stereotaxic injection of the Anti-DAT-Saporin into the striatum of female C57BL6 mice causes a progressive reduction in the numbers of DA neurons in the SN in comparison to the non-lesioned hemisphere, and sham controls. Furthermore, in parallel to the immunohistochemical dopamine neuron death, the animals display a pronounced circling behaviour when challenged with apomorphine (6mg/kg). This model is akin to the gradual deterioration of the nigro-striatal system that occurs in Parkinson’s Disease and provides a system to intervene at various stages of dopamine neuron loss and evaluate the effectiveness of stem cell therapy.

Related Products: Anti-DAT-SAP (Cat. #IT-25)

Impact of 192 IgG-saporin medial septum lesions on working memory

Pizzo DP, Samadzadeh L, Thal LJ, Frielingsdorf H (2004) Impact of 192 IgG-saporin medial septum lesions on working memory. Neuroscience 2004 Abstracts 436.1. Society for Neuroscience, San Diego, CA.

Summary: It is generally believed that cholinergic input to the hippocampus (hpc) is involved in learning and memory. The objective of the present study was to clarify whether working memory as assessed by the Morris water maze (mwm) is impaired by selective lesions of the cholinergic cells in the medial septum in adult male rats using 75 ng192IgG-saporin per side. Two weeks post-lesion, naive and lesioned rats were trained in the mwm task focusing on working memory, which was tested using a new platform location every day. The difference (improvement) in latency between trial 1 and 2 was used as an index of working memory function. Nine different platform locations were tested. The locations yielding the highest group difference were retested, with increasing intertrial intervals (ITI) from 30 min to 24 h between the 1st and 2nd trial. In a majority of the trial blocks there was a trend suggesting that lesioned rats had impaired working memory, however there was no consistent significant difference between groups in any of the tasks. To potentially further separate the groups rats were then infused with nerve growth factor (NGF; 5 µg/day), or vehicle into the ventricular system. After 17 days of infusion working memory was retested, however NGF treatment did not affect performance. The lesions were complete as measured by loss of choline acetyltransferase activity (ChAT) to less than 10% of levels of the naive, vehicle treated rats. NGF infusion increased hpc ChAT activity in naive but not in lesioned rats. In conclusion, selectively reducing ChAT activity by more than 90% in the hpc is not sufficient to significantly impair working memory as assessed by the mwm. We cannot exclude that a more sensitive working memory task would reveal a deficit in the lesioned animals, however it is also possible that intact septohippocampal cholinergic projections are not crucial for working memory function.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Cholinergic neurons in the basal forebrain participate in consciousness and general anesthesia

Leung LS, Petropoulos S, Ma J, Shen B (2004) Cholinergic neurons in the basal forebrain participate in consciousness and general anesthesia. Neuroscience 2004 Abstracts 565.4. Society for Neuroscience, San Diego, CA.

Summary: Acetylcholine (Ach) in the brain has long been associated with consciousness. In this study, we assessed consciousness in rats by their EEG and behavioral responses to a general anesthetic. Cholinergic neurons in the nucleus basalis of Meynert (NbM) were lesioned by bilateral injection of toxin IgG192-saporin (0.15 μg at P1.4, L2.7, 7.7 mm below dura) in 10 adult male rats. Control (5 rats) had saline injected into the NbM. EEGs were recorded by electrodes placed in layer V of the frontal cortex (FC) and visual cortex (VC). Spectral analysis of the spontaneous EEGs in FC and VC during awake-immobility indicated that lesioned animals showed higher delta (0.8 to 4 Hz) and lower gamma (30- 58 Hz) power as compared to controls. Subsequent acetylcholinesterase staining (optical density) confirmed significant Ach depletion in both FC and VC, in the lesion as compared to the control group (P<0.002, Wilcoxon). When challenged with a normally subanesthetic dose of general anesthetic, the lesioned rats showed, as compared to controls, significantly longer durations of loss of righting and tail-pinch response after 5 mg/kg i.v. propofol (P<0.001), but not after 20 mg/kg i.p. pentobarbital or 2% halothane. In correspondence with the deep behavioral anesthesia, delta power at FC after propofol was significantly larger in lesioned than control rats. Lesioned rats, as compared to controls, also showed decreased locomotion (behavioral excitation) when given 2% halothane in a large chamber. In summary, a loss of Ach in the neocortex decreases the level of consciousness as indicated by increased delta and decreased gamma EEG, and by an increased sedative/ anesthetic response to propofol i.v. We suggest that patients with Alzheimer disease may show altered response to some general anesthetics.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Cholinergic basal forebrain lesions disrupt acquisition of cued and uncued differential reinforcement of low rate responding

Corley SR, Atkinson M, Cabrera S, Castillo A, Crawford D, Kitto M, Butt AE (2004) Cholinergic basal forebrain lesions disrupt acquisition of cued and uncued differential reinforcement of low rate responding. Neuroscience 2004 Abstracts 436.10. Society for Neuroscience, San Diego, CA.

Summary: The frontal cortex, medial septum/vertical diagonal band (MS/VDB), and hippocampus have been implicated in supporting differential reinforcement of low rate responding (DRL) behavior in rats. Because the frontal cortex and hippocampus receive cholinergic input from the basal forebrain, we hypothesized that 192 IgG-saporin (SAP) lesions of the basal forebrain would disrupt DRL acquisition in the current experiment. To distinguish between potential deficits in timing, as opposed to impairments in response inhibition, we trained rats in either the standard DRL task (which requires both timing of behavior and response inhibition) and on a cued version of the task (which does not require the ability to time behavior but does require response inhibition). Rats were first shaped to bar press before receiving either bilateral SAP lesions of the basal forebrain or sham lesions. Rats were returned to bar press training for 5 more days. Rats were then shifted to a DRL 20 s, LH 10 s (limited-hold 10 s) schedule of reinforcement. Half of the rats were provided with a cue light signaling the availability of reinforcement, whereas the other half underwent standard DRL 20 s LH 10 s testing without the visual cue. Rats with basal forebrain lesions showed a transient impairment in response inhibition in both the standard and the cued version of the DRL task. Both lesion groups made more responses at short inter-response-intervals than controls across the first 15 test days, although this impairment attenuated by the 20th test day. These data suggest that the cholinergic basal forebrain is involved in learning to withhold responding during acquisition in DRL.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Effect of dehydroepiandrosterone sulfate on retention in passive avoidance in septal hippocampal cholinergic lesioned rats

Arshad S, Li P, Fitz NF, Johnson DA (2004) Effect of dehydroepiandrosterone sulfate on retention in passive avoidance in septal hippocampal cholinergic lesioned rats. Neuroscience 2004 Abstracts 436.11. Society for Neuroscience, San Diego, CA.

Summary: Infusions of 192 IgG-saporin (SAP) into the medial septum (MS) selectively destroys cholinergic neurons projecting to the hippocampus. Our previous study demonstrated that this lesion impairs retention but not acquisition of a passive avoidance (PA) task in rats. The present study determined whether the neurosteroid Dehydroepiandrosterone sulfate (DHEAS) (0, 1, 3, 10, 30 mg/ml) could reverse SAP induced impairments of PA retention. Male Sprague-Dawley rats were administered either SAP (.22μg/μl) or vehicle directly into the MS. Passive Avoidance training began 2 weeks later. Training consisted of placing the animal into the lighted chamber of the apparatus and then delivering a foot shock (.75mA, 1 sec), when the animal moved into the adjacent darkened chamber. Training was repeated until the animal avoided the dark chamber for 2 consecutive trials of 2 minutes duration. Retention (latency to crossover to the dark chamber) was tested after seven days. DHEAS was administered one hour prior to retention testing. Results showed a dose dependent increase in crossover latency in SAP treated animals. DHEAS treatment in control animals, however, resulted in a dose dependent decrease in crossover latency. Thus, DHEAS attenuated the impairment in retention in SAP treated animals with hippocampal cholinergic hypofunction, but impaired retention in cholinergically intact rats in PA.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Effects of dehydroepiandrosterone sulfate on delayed match to position T-maze task performance in 192- IgG saporin lesioned rats

Fitz NF, Li P, Johnson DA (2004) Effects of dehydroepiandrosterone sulfate on delayed match to position T-maze task performance in 192- IgG saporin lesioned rats. Neuroscience 2004 Abstracts 436.2. Society for Neuroscience, San Diego, CA.

Summary: Prior studies have shown that infusion of 192 IgG-saporin (SAP), a cholinergic neurotoxin, into the media septum (MS) of rats selectively lesions cholinergic neurons that project to the hippocampus, resulting in impaired acquisition of a delayed matching to position (DMP) T-maze task. Since the neurosteriod dehydroepiandrosterone sulfate (DHEAS), displayed memory enhancing properties in rodents, the present study investigated the effects of DHEAS administration on MS SAP lesioned animals. Male Sprague-Dawley rats received intraseptal infusions of either cerebrospinal fluid or SAP (0.22 μg/μl). Fourteen days later, the rats were administered IP injections of either DHEAS (20mg/ml) or vehicle one hour prior to DMP testing. During the acquisition phase of testing, each rat completed 8 trial pairs per day until reaching criterion (15 of 16 correct choices). Treatment with DHEAS resulted in a 10% shortening of the number of days to reach criterion in the SAP treated animals compared to SAP non-treated animals.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Hippocampal Arc and Homer 1a expression in behaviorally characterized 192 IgG-saporin lesioned rats

Fletcher BR, Guzowski JF, Baxter MG, Shapiro ML, Rapp PR (2004) Hippocampal Arc and Homer 1a expression in behaviorally characterized 192 IgG-saporin lesioned rats. Neuroscience 2004 Abstracts 436.4. Society for Neuroscience, San Diego, CA.

Summary: Fornix lesions impair hippocampal dependent learning and block behavioral induction of the immediate-early gene Arc. The present experiment tested the role of cholinergic innervation in the transcriptional induction of the activity related immediate-early genes Arc and Homer 1a. 192 IgG-saporin or vehicle was injected into the medial septal nucleus and vertical diagonal band. Behavioral characterization on cued and spatial delayed match-to-place tasks in a radial arm water maze revealed an impairment in cognitive flexibility, but not spatial memory in lesioned animals. Immediately after animals explored two novel environments their brains were processed for fluorescence in situ hybridization with probes for Arc and Homer 1a to reveal the recent activation history of individual neurons. Confocal stereological quantification of labeling in the CA1 and CA3 cell fields of the hippocampus revealed no dramatic difference in number of positive cells between groups. These results show that, unlike fornix lesions, cholinergic denervation of the hippocampus is not sufficient to block behavioral activation of Arc or Homer 1a transcription. Therefore, cholinergic innervation is not required for Arc or Homer 1a expression.

Related Products: 192-IgG-SAP (Cat. #IT-01)

192 IgG-saporin lesions of the nucleus basalis magnocellularis impair biconditional discrimination learning in rats

Kitto MR, Carbrera S, Corley S, Castillo A, Atkinson M, Andrews C, Casteneda M, Crawford D, Iliscupidez M, Monahan R, Rodriguez D, Salley T, Butt AE (2004) 192 IgG-saporin lesions of the nucleus basalis magnocellularis impair biconditional discrimination learning in rats. Neuroscience 2004 Abstracts 436.5. Society for Neuroscience, San Diego, CA.

Summary: Previous results from our laboratory suggest that the cholinergic nucleus basalis magnocellularis (NBM) is involved in configural association learning but not in simple association learning. In the current experiment, we hypothesized that 192 IgG-saporin lesions of the NBM in rats would impair biconditional visual discrimination learning, which requires configural association learning. In contrast, we hypothesized that NBM lesions would not impair acquisition of a simple visual discrimination, which requires only simple association learning. In Problem 1, rats were trained in a T-maze to solve a simple visual discrimination between a food-reinforced black goal arm (B+) and a non-reinforced white arm (W-), where the start arm of the maze was always striped (S). Next, in Problem 2, the reinforcement contingencies of the goal arms were reversed (W+ vs. B-), and the start arm visual cue was changed to gray (G). Finally, rats underwent biconditional discrimination training where half of the trials were of Problem 1 type and half were of Problem 2 type. Separately, Problems 1 (S: B+ vs W-) and 2 (G: W+ vs B-) can be solved using simple associations. However, in the biconditional discrimination, where Problems 1 and 2 are intermixed, configural association learning is required. Preliminary results supported our hypotheses. Acquisition of Problems 1 and 2, the simple association problems, did not differ between the NBM lesion group and the control group. However, performance in biconditional discrimination was impaired in the NBM lesion group compared to controls. These results are consistent with the argument that the NBM is involved in configural but not simple association learning.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Effects of neonatal cholinergic lesions on fear conditioning in 18-day-old rats

Ricceri L, Scattoni ML, Cutuli D, Calamandrei G (2004) Effects of neonatal cholinergic lesions on fear conditioning in 18-day-old rats. Neuroscience 2004 Abstracts 436.9. Society for Neuroscience, San Diego, CA.

Summary: We have previously shown that neonatal intracerebroventricular (icv) injections of the selective cholinergic immunotoxin 192 IgG-saporin on postnatal day (pnd) 7 induces behavioural alterations already detectable in the third postnatal week. In the present study we injected 192 IgG-saporin icv, in the nucleus basalis magnocellularis (nbm) or in the medial septum (ms) in 7-day-old rats and we then analysed fear conditioning on pnd 18. Fear conditioning to both auditory cue and environmental context was evident in both control and lesioned rats on pnd 18. However, conditioning to the environmental context (measured by freezing duration) was significantly more marked in icv and MS lesioned rats, whereas no effect of the cholinergic lesion was evident on conditioning to the auditory cue. These results suggest that neonatal removal of the cholinergic input to the hippocampal region paradoxically facilitates processing of spatial information in young rats.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Exercise accelerates relapsing paralysis after recovery from spinal demyelination

Ohara PT (2004) Exercise accelerates relapsing paralysis after recovery from spinal demyelination. Neuroscience 2004 Abstracts 419.6. Society for Neuroscience, San Diego, CA.

Summary: Exercise has been used to improve motor performance in humans and animals following spinal cord injury. The effects of exercise are generally positive but it is not known whether exercise is universally beneficial, particularly in rat models of spinal injury. We examined the spinal cord morphology and motor function recovery for 18 months in rats that had undergone lumbar spinal demyelination induced by CTB-saporin. Following the initial demyelination and paraplegia, motor function recovered and was stable for up to nine months after which there occurred a slow deterioration of function that occurred earlier and was more severe in rats that had been exercised on a treadmill. Rats given treadmill exercise starting three weeks after toxin injection had a mean motor deficit score of 3.0 (i.e. paraplegia) at perfusion while the non-treadmill treated rats had a mean score of 1.8 (SD 0.38, n = 6, p<0.05). Histological examination showed the same morphological changes occurred in both exercise and non-exercise treated animals including the loss of motoneurons, loss of spinal white matter and appearance of large spheroids of calcium in the ventral and dorsal horns and occasionally in the white matter. These findings suggest that, in addition to the acute effects of the toxin induced demyelination from which there is recovery of motor function, there are chronic irreversible effects of the toxin, or the initial demyelination, that cause a slow progressive degeneration of the spinal cord. This model might therefore be useful to study the long term effects of spinal insult of the type associated with conditions such as post-polio syndrome.

Related Products: CTB-SAP (Cat. #IT-14)

Electrophysiological profile of IgG192saporin-lesioned rats in the pilocarpine model of epilepsy

Benassi SK, Blanco MM, Mello LE (2004) Electrophysiological profile of IgG192saporin-lesioned rats in the pilocarpine model of epilepsy. Neuroscience 2004 Abstracts 452.14. Society for Neuroscience, San Diego, CA.

Summary: In order to investigate the importance of the basal forebrain cholinergic reorganization to the epileptogenesis process, adult male Wistar EPM-1 rats (180-220g) were subjected to status epilepticus (SE) induction by pilocarpine injection (320mg/kg, i.p.), after cholinergic lesion through IgG192-saporin (5μg/5μL, i.c.v.). Two months after SE induction animals were deeply anesthetized (choral hydrate 400 mg/kg, i.p.) and subjected to the electrical stimulation of the right CA3 and recorded (3M NaCl, 1MΩ) in the contralateral (left) CA1 region. Histological analysis included Nissl staining for the location of stimulating and recording electrodes and histochemistry for acetylcholinesterase (AChE) for the assessment of IgG192-induced lesions. The administration of the IgG192-saporin consistently and specifically diminished AChE staining in the hippocampus and neocortex while not affecting other brain areas (e.g., amygdala, striatum, etc). As compared to naive control animals, pilocarpine-treated animals generally showed loss of paired-pulse inhibition and the presence of multiple population spikes. Epileptic animals that were pre-treated with the cholinergic toxin did not differ from untreated epileptic animals in terms of paired-pulse inhibition or the presence of multiple population spikes. Large paired-pulse facilitation (P2>10 P1) for interstimulus intervals varying from 20 to 200 ms was encountered for both groups of epileptic animals with no distinction between each other. We suggest that the basal forebrain cholinergic system does not have a major role in defining the hyperexcitability of hippocampal circuits in the pilocarpine model of epilepsy.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Decreased number of sighs and post-sigh apneas indicates neuronal degeneration within the preBötzinger complex

Janczewski WA, McKay LC, Feldman JL (2004) Decreased number of sighs and post-sigh apneas indicates neuronal degeneration within the preBötzinger complex. Neuroscience 2004 Abstracts 424.10. Society for Neuroscience, San Diego, CA.

Summary: Sighs, also known as augmented or deep breaths, are inspiratory efforts of increased tidal volume, duration and biphasic shape. Sighs occur periodically in most mammals and are present throughout life, even in utero. Some sighs are followed by a post-sigh apnea lasting longer than 2 average respiratory periods. In adult rats, the number of sighs per hour [sigh index (SI)] is ~20. When we injected 0.2 pmol of substance P (SP) into the preBötzinger Complex, SI increased to >100, suggesting that activation of preBötzinger Complex NK1 receptor expressing (NK1R) neurons produces sighs. We hypothesized that degeneration of preBötzinger Complex NK1R neurons would decrease SI and eliminate post-sigh apneas. We injected the toxin saporin conjugated to SP bilaterally into the preBötzinger Complex to selectively destroy NK1R neurons. The number of ablated NK1R neurons increased from days 2-6 postinjection. In all rats at days 2-3, SI dropped below 5 and all post-sigh apneas were eliminated. In one group of rats (n=6), an ataxic breathing pattern developed, resulting from >90% NK1R cell loss. In these rats, all sighs were eliminated from days 3-4 postinjection. A second group of rats (n=5) maintained a eupneic breathing pattern. They were observed for two months postinjection and did not recover the preinjection sigh pattern. Their NK1R cell loss was <80% after two months, but must have been smaller at day 2 postinjection when their sigh pattern changed. We hypothesize that a modest (<< 80%) decrease in the number of NK1R neurons within the preBötzinger Complex, due to a toxin here but otherwise due to aging or neurodegenerative processes, may explain the decrease in SI seen with age in humans. We postulate that a marked decrease in the number of sighs and post-sigh apneas is an early symptom of neurodegeneration within the preBötzinger Complex.

Related Products: SP-SAP (Cat. #IT-07)

Investigation of the functional role of non-peptidergic primary afferent sensory fibres in the transmission of pain related information

Bailey AL, Bennett G, Ribeiro-da-Silva A (2004) Investigation of the functional role of non-peptidergic primary afferent sensory fibres in the transmission of pain related information. Neuroscience 2004 Abstracts 484.1. Society for Neuroscience, San Diego, CA.

Summary: It is well established that small diameter, unmyelinated, primary afferent C-fibres can be divided into two neurochemically defined populations, one that contains neuropeptides such as Substance P (SP) and Calcitonin-gene related peptide (CGRP) and the other which binds Isolectin B4 (IB4) and is relatively peptide negative. A great deal of circumstantial evidence indicates that the non-peptidergic afferents play a functionally distinct role in pain transmission compared to peptidergic afferents. Indeed, the concept of two distinct subpopulations of C-fibres would indicate the occurrence of parallel processing in pain pathways. However, the functional role of non-peptidergic afferents in the transmission of pain-related information is still unclear. In an attempt to clarify their functional role, we decided to study the development of hyperalgesia and allodynia in adult male Sprague-Dawley rats with selective ablation of IB4-binding, non-peptidergic afferent input to the dorsal horn. To achieve this, we injected IB4 conjugated to Saporin (SAP) into the left sciatic nerve and examined both neurochemical and behavioural changes over a month’s time. Our data show that following injection of the toxin conjugate, IB4-labelling, P2X3-immunopositive fibre terminals disappear from a band in the superficial dorsal horn that expands over a two week period until it comprises most of the mediolateral extent of the dorsal horn. Behavioural data indicates that there are transient changes in acute pain thresholds to mechanical and thermal stimuli. Changes in pain thresholds in animals lacking non-peptidergic input into the spinal dorsal horn in an animal model of Complete Freund’s Adjuvant (CFA) induced inflammation will also be presented.

Related Products: IB4-SAP (Cat. #IT-10)

Ablation of NK1 receptor-expressing (NK1R) neurons within the preBötzinger complex (preBötC) in adult rats disrupts breathing during sleep before affecting breathing in wakefulness.

McKay LC, Janczewski WA, Feldman JL (2004) Ablation of NK1 receptor-expressing (NK1R) neurons within the preBötzinger complex (preBötC) in adult rats disrupts breathing during sleep before affecting breathing in wakefulness. Neuroscience 2004 Abstracts 424.9. Society for Neuroscience, San Diego, CA.

Summary: In adult rats, as the number of ablated preBÖtC NK1R neurons increases, eupnea is progressively disrupted during wakefulness, eventually resulting in an ataxic breathing pattern when cell loss is >80% (Gray et al. Nat. Neurosci. 2001). Is there a disruption of breathing during sleep prior to a disruption of breathing in wakefulness? Adult male Sprague Dawley rats (n=4) were instrumented to record: diaphragmatic, abdominal and neck EMG; ECG, and; EEG. Subsequently, the toxin Saporin conjugated to Substance P was injected bilaterally into the preBÖtC to selectively destroy NK1R neurons. Rats were monitored from day 1 postinjection until they were sacrificed between days 9-15. On days 3-4, changes in breathing pattern were observed during REM sleep. These changes were characterized by an increase in frequency of central apneas (4-7/hour vs 2/hour preinjection controls; p<0.05) and an increase in apnea length (3-6 sec vs 1-2 sec preinjection controls; p<0.05). On days 4-6, the onset of REM sleep typically induced hypopnea and a central apnea resulting in an arousal to wakefulness within 4-10 sec and the reestablishment of a normal breathing pattern. Eupnea was maintained during wakefulness; in some cases there was an increase in frequency compared to preinjection controls (183 vs 120 breaths/min). From day 6 onwards, breathing rhythm was progressively disrupted until an ataxic breathing pattern developed during wakefulness (~day 8). At this stage, rats were unable to sleep because breathing stopped upon sleep onset. In all cases, lesion extent at sacrifice, as determined by histology, was confined to the preBÖtC and >80% of NK1R neurons were destroyed. The spreading ablation of preBÖtC NK1R neurons results in a progressive disruption in breathing pattern, initially during sleep leading to pathological disturbances of breathing in both sleep and wakefulness.

Related Products: SP-SAP (Cat. #IT-07)

Effects of cholinergic deafferentation of prefrontal cortex on working memory: A convergence of behavioral and modeling results

McGaughy JA, Koene R, Eichenbaum HB, Hasselmo ME (2004) Effects of cholinergic deafferentation of prefrontal cortex on working memory: A convergence of behavioral and modeling results. Neuroscience 2004 Abstracts 551.7. Society for Neuroscience, San Diego, CA.

Summary: In humans, the prefrontal and medial temporal lobe areas are differentially activated during working memory dependent upon the whether stimuli are familiar or novel. Prefrontal activation occurs with highly familiar stimuli whereas the medial temporal lobe is activated by novel stimuli (Stern, et al. Hippocampus v. 11, 2001). The maintenance of novel information in the entorhinal cortex (EC) is hypothesized to depend upon self-sustained spiking activity in single neurons produced by cholinergic activation of muscarinic receptors (Klink and Alonso, J. Neurophys. 77, 1997). The current study investigated whether cholinergic modulation of the prefrontal cortex regulates sustained spiking activity for familiar stimuli. Rats were trained in an odor-cued delayed non-matching to sample task. After reaching asymptotic performance, rats were infused bilaterally with either 192 IgG-saporin (SAP) or its vehicle into the prefrontal cortex(PFC;0.01μg/μl;1.0μl/injection). Following PFC-SAP lesions,rats were impaired in working memory with highly familiar odors when choice stimuli were probed sequentially but not simultaneously. Though PFC-SAP rats reliably sampled both choices, they failed if the first cup probed matched the sample. PFC-SAP rats were also unable to maintain multiple items in memory. These impairments cannot be explained by the loss of response inhibition, the conditional response rule, attentional or sensory abilities. It is hypothesized that in the absence of a functional frontal cortex, the PFC-SAP rats relied on the EC. Computational modeling of EC suggests repetitions of an odor or the presentations of multiple odors disrupt the pattern of self-sustained spiking in this area and, thus, the representation of the stimulus. These data elucidate the interplay between the PFC and EC during a working memory task.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Intrathecal galanin-saporin and NPY-saporin reduce nocifensive responses to noxious heat and formalin

Wiley RG, Kline IV, RHLappi DA (2004) Intrathecal galanin-saporin and NPY-saporin reduce nocifensive responses to noxious heat and formalin. Neuroscience 2004 Abstracts 292.15. Society for Neuroscience, San Diego, CA.

Summary: Although the precise circuitry of the dorsal horn underlying nociception is not fully understood, there is evidence that regulation of the excitability of nociceptive projection neurons is influenced/modulated by excitatory interneurons. The present study sought to determine if selectively destroying presumed excitatory interneurons in the superficial dorsal horn would alter nocifensive responses to noxious thermal or chemical stimuli. The strategy chosen was to inject saporin (sap) conjugates of either galanin (GAL) or neuropeptide Y(NPY) into the lumbar subarachnoid space and then test rats on the hotplate and observe the nocifensive responses to hindpaw formalin injection. After hotplate testing for 2 weeks, staining for c-fos expression in the dorsal horn was performed 2 hrs after hindpaw formalin injection. Lumbar intrathecal injection of 500 ng of either GAL-sap or NPY-sap produced no obvious change in appearance, body weight or spontaneous activity of adult male Sprague-Dawley rats. Both toxins reduced responses on the 44 C hotplate but not at 52 C. Nocifensive responses to the 47 C hotplate also were reduced but not as strikingly as at 44 C. Responses to hindpaw formalin were remarkably different. Toxin-injected rats held the injected foot close to the body, off the floor, throughout the 90 minute observation period but otherwise ignored the injected paw. Unlike controls, toxin-injected rats did not shake, lick or bite the injected hindpaw and showed normal exploratory behavior. These results are interpreted as showing that these two toxins likely destroy excitatory interneurons in the superficial dorsal horn resulting in decreased excitability of nociceptive projection neurons, and therefor reduced sensitivity to noxious thermal and chemical stimuli.

Related Products: NPY-SAP (Cat. #IT-28), Galanin-SAP (Cat. #IT-34)

Behavioral evidence for a capsaicin-sensitive inhibitory pathway (CSIP): A novel modulatory role for substance P

King CD, Baker B, Gu JG, Vierck CJ, Yezierski RP (2004) Behavioral evidence for a capsaicin-sensitive inhibitory pathway (CSIP): A novel modulatory role for substance P. Neuroscience 2004 Abstracts 292.18. Society for Neuroscience, San Diego, CA.

Summary: Exposure to noxious thermal stimulation or application of capsaicin cream causes the release of SP from capsaicin-sensitive primary afferent terminals that activate neurokinin-1 receptor (NK1R) expressing neurons in the superficial dorsal horn. Recent evidence suggests the existence of a capsaicin-sensitive inhibitory pathway (CSIP), a novel inhibitory mechanism that involves NK1R expressing neurons in laminae III-V. To determine the functional significance of these NK1R expressing neurons, substance P-saporin neurotoxin (SP-SAP) was used to ablate NK1R neurons in the superficial laminae. Elimination of the NK1R neurons in this region made it possible to evaluate the modulatory effects of NK1R expressing inhibitory neurons in deeper laminae. Reflexive responses were evaluated in rats during a 10-minute trial at 44.5°C before (pre-) and 14 days after (post-) intrathecal injection of 350ng SP-SAP. Testing conditions included: 1) baseline; 2) hindpaw application of 1% capsaicin cream; and, 3) intrathecal injection of the NK1 antagonist CP-97,345 following hindpaw application of 1% capsaicin cream. In normal rats, hindpaw application of capsaicin produced thermal hyperalgesia. In contrast, application of capsaicin produced a hypoalgesia in the same rats after treatment with SP-SAP. The capsaicin-induced hyperalgesia in normal rats was blocked by CP-97,345. The antagonist also blocked the capsaicin-induced hypoalgesia in SP-SAP rats. In conclusion, it is suggested that substance P activates inhibitory interneurons in the deep dorsal horn. The inhibitory effect initiated by substance P on pain transmission neurons represents a novel role of substance P in the spinal processing of nociceptive information.

Related Products: SP-SAP (Cat. #IT-07)

Altered effects of systemic bicuculline on intensity-dependent c-Fos expression in rats ablated with NK-1 receptor-bearing neurons in the trigeminal caudal nucleus

Abe T, Shimoda T, Sugiyo S, Ohshita N, Takao T, Takemura M (2004) Altered effects of systemic bicuculline on intensity-dependent c-Fos expression in rats ablated with NK-1 receptor-bearing neurons in the trigeminal caudal nucleus. Neuroscience 2004 Abstracts 294.12. Society for Neuroscience, San Diego, CA.

Summary: In rats pretreated with saporin conjugated to substance P (SP-Sap: 5 μM, 5 μl) into cisterna magna, the numbers of neurons-immunoreactive for NK-1 receptor (NK-1R) in laminae I and III of trigeminal caudal nucleus (Vc) were significantly decreased compared with rats similarly treated with saline (Sal; 5 μl) or blank-saporin (Bl-Sap; 5 μM, 5 μl). We examined the effects of selective ablation of NK-1R-bearing neurons and systemic administration of bicuculline (2 mg/kg, i.p.) on the expression of c-Fos induced 2 hr after electrical stimulation (5 Hz, 5 ms) of the trigeminal ganglion (TG) at low (0.1 mA) and high intensities (1.0 mA). In Sal- or Bl-Sap treated rats, 10 min stimulation at 0.1 and 1.0 mA of the TG induced c-Fos-immunoreactive (c-FosIR) cells in the ipsilateral superficial layers of the Vc (VcI/II) in a intensity-dependent manner. In rats treated with SP-Sap, and stimulated at 1.0 mA but not at 0.1 mA, the numbers of c-FosIR cells in the Vc were significantly decreased compared to Sal- or Bl-Sap treated rats. In Sal- or Bl-Sap treated rats preadministed with bicuculline and stimulated at 0.1 mA and 1.0 mA, the numbers of c-FosIR cells in VcI/II were significantly increased and decreased, respectively. However, in SP-Sap treated rats preadministered with bicuculline and stimulated at 0.1 mA and 1.0 mA, the numbers of c-FosIR cells in VcI/II were significantly increased. These results indicate that NK-1R-bearing neurons in the Vc have pivotal role in the modality and/or intensity-dependent sensory (nociceptive) processing in the TSN through GABAA receptors.

Related Products: SP-SAP (Cat. #IT-07)

The effects of chronic deafferentation and SSP-saporin on pain responses, spinal cord neurons and on the structure and function of the somatosensory thalamus (VPL) in the macaque monkey

Ralston HJ, Wiley RG, Dougherty PM, Weng HR, Cata J, Chen JH, Hopkins SD, Canchola SA, Galo E, Vierck CJ (2004) The effects of chronic deafferentation and SSP-saporin on pain responses, spinal cord neurons and on the structure and function of the somatosensory thalamus (VPL) in the macaque monkey. Neuroscience 2004 Abstracts 295.1. Society for Neuroscience, San Diego, CA.

Summary: We have used behavioral, physiological and anatomical methods to examine the effects of chronic (> 2 years) lesions of the dorsal column pathway and of the intrathecal administration of the neurotoxin SSP-saporin in adult M. arctoides. Normal animals were evaluated to determine their responses to noxious heat (52 to 58°C) applied to the lower limbs. Subsequently, the monkeys were anesthetized and had unilateral lesions of the dorsal and dorsolateral spinal cord white matter pathways at midthoracic levels. After recovering from the surgery, their pain responses were studied for more than 1 year, following which SSP-saporin was administered to the lumbosacral spinal cord. The animals were found to have a decrease in their responses to noxious heat applied to the lower limbs. Terminal physiological experiments revealed that the neurons within the lower limb representation of VPL on the side contralateral to the thoracic cord lesion did not have normal receptive fields, although some cells responded to stimulation of both upper and lower limbs. Histological sections of lumbar spinal cord were stained for neurokinin 1 receptor (NK-1R) and showed a significant decrease in lamina I NK-1R positive neurons. Electron microscopy of VPL revealed patterns of synaptic terminals that were different than those found in VPL of normal macaques. We will determine whether there is a significant correlation between the altered behaviors and the physiological and anatomical changes in these animals as a consequence of somatosensory deafferentation.

Related Products: SSP-SAP (Cat. #IT-11)

Mu-opioid receptor-expressing neurons in the nucleus reticularis gigantocellularis contribute to descending facilitation during the development of inflammatory pain

Wei F, Zou S, Robbins MT, Ren K, Dubner R (2004) Mu-opioid receptor-expressing neurons in the nucleus reticularis gigantocellularis contribute to descending facilitation during the development of inflammatory pain. Neuroscience 2004 Abstracts 297.3. Society for Neuroscience, San Diego, CA.

Summary: We have previously shown that nucleus reticularis giangocellularis (NGC) is involved in descending facilitation of inflammatory hyperalgesia. The cellular mechanisms of descending facilitation from the NGC are unknown. The targeted destruction of the mu-opioid receptor-containing neurons in the rostral ventromedial medulla (RVM) by a dermorphin-saporin conjugate prevents nerve injury-induced hyperalgesia in rats (Porreca et al., J. Neurosci. 21:5281, 2001). We examined the effects of selective deletion of the mu-opioid receptor-expressing neurons in the sub-regions of RVM on nocifensive behaviors in rats. After microinjection of dermorphin-saporin conjugate (1.5 pmol/500 nl) into the RVM, there were no changes in baseline thermal and mechanical sensitivity to noxious stimuli. However, the injection of dermorphin-saporin conjugate into bilateral NGC (n=7) significantly attenuated the thermal hyperalgesia and mechanical allodynia at 30 min to 1 d after hindpaw inflammation produced by injection of complete Freund’s adjuvant, compared to sham (blank-saporin or dermorphin) groups (n=3-6). The lesion of the nucleus raphe magnus (NRM) (n=3) only slightly reduced hyperalgesia at 3 h after inflammation. The loss of NGC mu-opioid receptor-containing neurons also decreased nocifensive behaviors only in phase II of the formalin model. In contrast, NRM lesions were without an effect on formalin-induced phase I/II responses. These findings indicate that selective deletion of the mu-opioid receptor-containing neurons in the nucleus reticularis giangocellularis attenuates inflammatory hyperagesia and allodynia.

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Prevention of depletion-induced motoneuron dendritic atrophy requires testosterone effects on target musculature

Fargo KN, Sengelaub DR (2004) Prevention of depletion-induced motoneuron dendritic atrophy requires testosterone effects on target musculature. Neuroscience 2004 Abstracts 310.10. Society for Neuroscience, San Diego, CA.

Summary: Motoneurons in the spinal nucleus of the bulbocavernosus (SNB) in male rats project to the penile muscles bulbocavernosus (BC) and levator ani (LA). These motoneurons share a midline location, have intermingled somata, extensive dendritic overlap, and common afferents, and organize coordinated contractions of the penile musculature. Unilateral depletion of BC-projecting motoneurons causes marked dendritic atrophy in contralateral BC-projecting motoneurons, and this atrophy can be prevented with testosterone (T) treatment. In this experiment, we test whether the depletion-induced atrophy is related to the innervation of homotypic muscles. BC-projecting motoneurons were depleted by unilateral injection with saporin conjugated to the cholera toxin B subunit (SAP); some animals were simultaneously treated with T. Four weeks later, a period demonstrated to be sufficient to observe dendritic atrophy in remaining motoneurons, HRP conjugated to the cholera toxin B subunit (BHRP) was injected into the ipsilateral LA. SAP injection into the BC muscle killed over 40% of ipsilateral SNB motoneurons. Dendritic length in LA-projecting motoneurons was reduced by almost 60%. Because the SAP-induced depletion of motoneurons and the resultant dendritic atrophy occurred across motor populations, this result indicates that the dendritic atrophy we have observed previously is not restricted to motoneurons projecting to homotypic muscles. In previous studies, prevention of dendritic atrophy by T treatment in BC-projecting motoneurons was accompanied by a marked hypertrophy of the BC muscle. In the present experiment, T treatment failed to prevent dendritic atrophy in LA-projecting motoneurons, and further did not result in hypertrophy of the LA ipsilateral to the SAP-injected BC. Thus, it appears the neuroprotective effect of T treatment on SNB motoneurons may be dependent on T effects in the target musculature.

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Neuronal correlates of signal detection in rat posterior parietal cortex

Broussard JI, Sarter M, Givens B (2004) Neuronal correlates of signal detection in rat posterior parietal cortex. Neuroscience 2004 Abstracts 331.6. Society for Neuroscience, San Diego, CA.

Summary: The posterior parietal cortex (PPC) has been shown to be involved in the attentional processing of visual stimuli. Recent evidence has indicated that neuronal activity in the PPC is increased during the detection of signals, and this activation is modulated by visual distractors. We tested the hypothesis that detected signals are associated with increased PPC unit activity. Animals were trained in a sustained attention task using signal and nonsignal trials. After training to criterion (>75% accuracy), we implanted moveable stereotrodes into the PPC. A visual distractor was presented in a block of trials during testing sessions and effects on performance and single unit activity were examined. We also evaluated the effects of varying signal duration on performance and single unit activity. PPC neurons (39/111) exhibited a significantly greater response during signal trials than during nonsignal trials. The presentation of visual signals produced a robust increase in neuronal activity prior to the performance of a hit, but not prior to a miss, both of which required a lever press. Analysis of signal duration indicated that shorter signals resulted in fewer hits. PPC neurons became active when the signal was accurately detected, independent of signal duration. Shorter signals activated the PPC on fewer trials, which was associated with a lower likelihood for detection. The visual distractor reduced both the signal-driven unit activity and the relative number of hits. These findings suggest that activation of the PPC is associated with the detection of visual signals. We are currently investigating the effects of local cholinergic deafferentation (via 192 IgG saporin) on signal driven neuronal activity in the PPC. These studies will elucidate the contribution of basal forebrain cholinergic innervation to attentional processing in the PPC.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Brainstem catecholaminergic neurons participate in central chemoreception in NREM sleep and wakefulness

Nattie EE, Li A (2004) Brainstem catecholaminergic neurons participate in central chemoreception in NREM sleep and wakefulness. Neuroscience 2004 Abstracts 145.9. Society for Neuroscience, San Diego, CA.

Summary: In the locus ceruleus (LC), noradrenergic neurons are CO2 sensitive in vitro and focal acidification stimulates breathing in vivo. Do catecholaminergic (CA) neurons in general have a like role? To kill brainstem CA neurons we administered a conjugate of the cell toxin saporin with an antibody to dopamine-β-hydroxylase via the fourth ventricle in rats (N=7) using IgG-saporin conjugate injections as a control (N=6). We studied breathing in air, 3 and 7% CO2 during NREM sleep and wakefulness before and 7, 14, and 21 days after the injections. TH-ir noradrenergic neurons were significantly reduced in LC (-84%) and the A5 region (-78%) but not the A9 region. PNMT-ir adrenergic neurons were significantly reduced in C3 (-56%) and C1 (-60%) regions. Neither treatment affected room air breathing. In 3 and 7% CO2, IgG-SAP injections had no effect. In the lesion group, during 3% CO2 frequency (f) was significantly decreased (two-way ANOVA) and Δ ventilation (VE) (VE in 5% CO2 – VE in air) was significantly decreased in sleep. During 7% CO2, both absolute and Δ VE and f were significantly decreased in sleep and wakefulness, Δ VE by 25% in wakefulness and 28% in sleep at 21 days. Brainstem CA neurons participate in central chemoreception in vivo during both NREM sleep and wakefulness.

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Neurotoxic lesions of serotonin containing cells of the median raphe nucleus produce constant hippocampal theta rhythm in behaving rats

Sundararaman N, Vertes RP, Perry GW (2004) Neurotoxic lesions of serotonin containing cells of the median raphe nucleus produce constant hippocampal theta rhythm in behaving rats. Neuroscience 2004 Abstracts 196.15. Society for Neuroscience, San Diego, CA.

Summary: The median raphe nucleus (MR) is a major serotonin containing cell group with pronounced projections to the forebrain. The MR exerts strong desynchronizing actions on the EEG activity of the hippocampus. MR stimulation desynchronizes the hippocampal EEG (or blocks theta), and electrolytic MR lesions produce continuous theta. Evidence suggests that desynchronizing actions of MR on the hippocampal EEG are mediated by serotonergic (5-HT) cells of MR. Injections of pharmacological agents into MR that suppress 5-HT MR activity generate theta at short latencies and for long durations. We examined the effects of the selective destruction of 5-HT cells of MR using the 5-HT neurotoxin, anti-SERT-SAP (Advanced Targeting Systems) on the EEG activity of the hippocampus in behaving rats. Under deep sodium pentobarbital anesthesia, rats were chronically prepared with bipolar electrodes, bilaterally in the dorsal hippocampus, a cortical screw for recording the cortical EEG and an indwelling cannula placed 3-4 mm dorsal to MR for the injection of anti-SERT-SAP into MR. Following a 5-7 day period of recovery, hippocampal EEG activity was recorded daily for 7 days as rats freely moved about in a shielded enclose, and then re-assessed under the same conditions following neurotoxic lesions. We found that neurotoxic lesions of MR that resulted in a substantial destruction of 5-HT MR cells (80-90%) produced a continuous theta rhythm in rats; that is, during locomotor behavior as well as during states when theta is normally absent, such as immobility and grooming. For some rats, theta was equivalent during complete immobility and active movement. These results support earlier findings that 5-HT cells of MR are directly involved in the desynchronization of the hippocampal EEG, and indicate that the MR exerts a powerful modulatory influence on the hippocampus.

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Estrogen supports structural plasticity of the basal forebrain cholinergic system in vivo

Saenz C, Dominguez R, de Lacalle S (2004) Estrogen supports structural plasticity of the basal forebrain cholinergic system in vivo. Neuroscience 2004 Abstracts 72.11. Society for Neuroscience, San Diego, CA.

Summary: It is known that estrogen (E2) modulates the structural plasticity of a variety of neurons, involving the activation of second messenger systems. We have previously described a strong E2-induced outgrowth in cholinergic neurons in vitro, and in the present study we follow up those results and examine E2’s ability to enhance cholinergic arborization in vivo, under several conditions. Twenty F344 female rats were used, 10 of them gonadectomized. All the rats received a unilateral lesion (200 nl of 192 IgG-saporin) into the left HDB, and a month later were randomly assigned to receive E2 or placebo via s.c. pellets for 60 days, at which point the rats were sacrificed, the brains prepared for histology and series of sections stained with an antibody against p75NTR. Sections were carefully matched across individuals, 10 neurons selected from both lesioned and intact HDB, and photographed. Neurons were chosen from the same area in all cases, located in the periphery of the HDB, where the neuritic arborization could be easily identified. Image analysis was performed using Metamorph software, on a predetermined set of parameters. Each image was the result of a stack of photographs taken at 2 µm intervals through the depth of the section. We compared mean neurite number per neuron and total neurite length per neuron, and found that in the healthy cholinergic neurons (control side), E2 contributed to a significant increase in neurite length and number. By contrast, no effect was found on cholinergic neurons from the lesioned side, showing that E2 cannot reverse the neuronal degeneration induced by the immunotoxin. These results are important in that they provide additional support to the hypothesis that E2 may be beneficial in preventing cholinergic degeneration, but no longer useful once neuronal damage has occurred.

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Loss of basal forebrain cholinergic neurons by 192 igG-Saporin induces increased IGF-II/M6P receptor expression in select brain areas

Hawkes CA, Kar S (2004) Loss of basal forebrain cholinergic neurons by 192 igG-Saporin induces increased IGF-II/M6P receptor expression in select brain areas. Neuroscience 2004 Abstracts 92.1. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is characterized neuropathologically by the presence of extracellular amyloid plaques, intracellular neurofibrillary tangles and neuronal loss in selected brain areas, including basal forebrain cholinergic neurons, which project to the hippocampus and neocortex. Increasing evidence supports a role of the endosomal-lysosomal (EL) system in the pathophysiology of AD. A key component of the EL system is the insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor, a single transmembrane domain glycoprotein which functions in the intracellular trafficking of lysosomal enzymes, and in the internalization of extracellular IGF-II and M6P-containing ligands. However, very little is known about the functional significance of this receptor in the brain. We examined expression of the IGF-II/M6P receptor and other markers of the EL system, at different time points following bilateral i.c.v. injection of 192 IgG-saporin. 192 IgG-saporin produced an almost complete loss of ChAT-positive neurons in the basal forebrain, as well as fibers in the hippocampus and frontal cortex, while striatal cholinergic neurons were unaffected. Western blotting and immunocytochemistry results indicate an upregulation of IGF-II/M6P receptor levels in the septum and frontal cortex. A modest increase was also observed in cathepsin D levels. The level of other EL markers, such as Rab5 and LAMP1, showed varied temporal and spatial changes. These results suggest that brain areas innervated by basal forebrain neurons, respond differently to the loss of cholinergic input and that elements of the EL system may be involved in cholinergic degeneration/compensatory responses of surviving neurons.

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Selective loss of basal forebrain cholinergic neurons by 192 IgG-saporin induces activation of glycogen synthase kinase-3β activity

Kar S, Hawkes C, Jhamandas JH (2004) Selective loss of basal forebrain cholinergic neurons by 192 IgG-saporin induces activation of glycogen synthase kinase-3β activity. Neuroscience 2004 Abstracts 92.2. Society for Neuroscience, San Diego, CA.

Summary: Glycogen synthase kinase-3β (GSK-3β) is a multifunctional enzyme involved in a variety of biological events including development, glucose metabolism and cell death. Its activity is negatively regulated by phosphorylation of Ser9 and upregulated by Tyr216 phosphorylation. Activation of GSK-3β induces apoptosis in a variety of cultured neurons and the inhibitory control of its activity by Akt kinase is one of the best characterized cell survival signaling pathways. In the present study, the cholinergic immunotoxin 192-IgG saporin was used to address the potential role of GSK-3β in the degeneration of the basal forebrain cholinergic neurons which are preferentially vulnerable in Alzheimer’s disease (AD) brain. Our results show that GSK-3β colocalizes with a subset of the forebrain cholinergic neurons and that loss of these neurons is accompanied by a transient decrease in phospho-Akt and phospho-Ser9 GSK-3β levels in the basal forebrain, hippocampus and the cortex. Neither total Akt, GSK-3β, nor phospho-Tyr216 GSK-3β levels were significantly altered in the aforesaid brain regions of treated animals. These results provide the very first evidence that increased GSK-3β activity is associated with in vivo degeneration of the forebrain cholinergic neurons and thus may be involved in the loss of these neurons as observed in AD brains.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Neurotrophic modulation of cholinergic denervation and hippocampal sympathetic ingrowth following immunolesioning with 192 IgG-saporin

Kolasa K, Parsons D, Conger K, Harrell LE (2004) Neurotrophic modulation of cholinergic denervation and hippocampal sympathetic ingrowth following immunolesioning with 192 IgG-saporin. Neuroscience 2004 Abstracts 92.9. Society for Neuroscience, San Diego, CA.

Summary: Injection of specific cholinotoxin, 192 IgG-saporin into the medial septum (MS)of rat induces not only a selective cholinergic denervation of hippocampus (CD),but an ingrowth of peripheral sympathetic fibers, originating from the superior cervical ganglion,into the hippocampus (HSI).A similar process,in which sympathetic noradrenergic axons invade hippocampus,may also occur in Alzheimer’s disease(AD). The severity of cognitive decline in AD patients has been linked to multiple factors including cholinergic and neurotrophic factors and their receptors, which undergo selective alterations throughout the progression of AD.It is known that the sites of neurotrophin synthesis in the septo-hippocampal system are predominantly hippocampal neurons. By using 192 IgG-saporin we have been able to mimic some of the cardinal features of AD e.x.cholinergic denervation and hippocampal sympathetic ingrowth and study their effect on growth factors in dorsal hippocampus. Thus,12 weeks after injection of 192 IgG-saporin we measured neurotrophic protein and mRNA expression using Western blot and RT-PCR techniques,respectively. Choline acetyltransferase activity(ChAT)and norepinephrine(NE) concentration was also detected.There was no change in NGF,BDNF,NT3,GDNF mRNA expression,but we have found significant decrease in 240 bp and increase in 328 bp of persephin mRNA expression in CD, and “normalization” in HSI group. No significant alteration was found in NGF and persephin protein expression, but significant decrease in mature form of BDNF protein expression was found in CD, with “normalization”in HSI group.Results of the study suggest that growth factors are affected by cholinergic denervation and may play an important role in regulation and development of HSI,which might be a beneficial phenomenon for restoration of at least some cognitive function.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Role of noradrenergic mechanisms in sustained attention, impulse control, and effects of methylphenidate in rats: Possible relevance to ADHD

Milstein JA, Lehmann O, Theobald DEH, Dalley JW, Robbins TW (2004) Role of noradrenergic mechanisms in sustained attention, impulse control, and effects of methylphenidate in rats: Possible relevance to ADHD. Neuroscience 2004 Abstracts 123.6. Society for Neuroscience, San Diego, CA.

Summary: There has been renewed interest in noradrenergic (NA) modulation of sustained attention and impulse control both clinically, with the approval of the SNRI atomoxetine for the treatment of attention deficit hyperactivity disorder, as well as preclinically, in the mediation of the psychomotor effects of stimulants, where blockade of α1 adrenoreceptors counteracts the locomotor stimulant effects of d-amphetamine. The current study examines the role of NA in the modulation of sustained attention and impulse control using the 5-choice serial reaction time task (5CSRT) in rats. Experiment 1 examined the systemic antagonism of methylphenidate (MP)-induced impulsivity with either prazosin, an α1 adrenoreceptor antagonist, which antagonises the locomotor activating effects of amphetamine, or propranolol, a general β-adrenoreceptor blocker. Prazosin partially attenuated the MP-mediated increase in premature responding, but also caused generalised motor slowing, increasing both correct latency as well as latency to collect food reward. Propranolol completely abolished MP-induced impulsivity. This effect was centrally rather than peripherally mediated, as nadolol, a peripheral β-blocker failed to affect MP-induced premature responding. Other experiments examined the comparative effects of selective dopaminergic or serotonergic receptor blockade. A second experiment investigated the effects of selective anti-DBH saporin-induced prefrontal NA depletion. Animals with prefrontal depletions were unimpaired on the baseline version of the 5CSRT. However, they appeared to be slightly impaired under high event rate conditions. Effects of selective prefrontal NA depletion on MP-induced behavioural changes will also be examined. Taken together, these studies provide evidence for a role of noradrenaline in impulse control and the effects of MP.

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