sfn2004

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)

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.

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

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

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)

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)

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)

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)

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)

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)

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)

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)