sfn2004

45 entries

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.

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

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.

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

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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ATS Poster of the Year Winner. Read the featured article in Targeting Trends.

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.

Related Products: CRF-SAP (Cat. #IT-13)

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.

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

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.

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

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.

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

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.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

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.

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

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