Abstracts from Society for Neuroscience (SFN) Symposium October 23-28, 1999 – Miami, Florida

Exciting New Advances in Pain Research and Treatment Using Receptor Internalization Technologies – SFN 1999 Symposium

16 entries found for : sfn1999

Cholinergic basal forebrain lesion results in reduced activity of neuronal NO synthase in hippocampal and neocortical areas of the rat brain.

Hartlage-Ruebsamen M, Lippe WR, Schliebs R (1999) Cholinergic basal forebrain lesion results in reduced activity of neuronal NO synthase in hippocampal and neocortical areas of the rat brain. Neuroscience 1999 Abstracts 847.3. Society for Neuroscience, Miami, FL.

Summary: Nitric oxide (NO) released by cortical neurons expressing the neuronal form of NO synthase (nNOS) is known to stimulate regional cerebral blood flow and is implicated in the formation of long term potentiation in the hippocampus. Cortical nNOS containing neurons express M] muscarinic acetylcholine receptors and receive cholinergic input from the basal forebrain (BF). Consequently, it has been shown that stimulation of BF cholinergic neurons leads to increased cortical perfusion. Cholinergic cell loss in the BF, reduced cortical blood flow and memory' dysfunction are characteristics of Alzheimer's disease. In the present study, we investigated the impact of a selective lesion of BF cholinergic neurons by the cholinergic toxin 192IgG-saporin on the expression and substrate binding activity of nNOS in selected regions of neocortex and hippocampus in the rat. While Western blot analysis yielded no significant changes in total nNOS protein levels 7 days post lesion, nNOS catalytic and substrate binding activity was reduced in a number of hippocampal and neocortical subregions as revealed by NADPH- diaphorase enzyme histochemistry and by quantitative autoradiography using [3H]L-A,’G-nitro-arginine binding. The data suggest that cholinergic mechanisms control, at least in part, neocortical and hippocampal nNOS activity providing further evidence for an NO-mediated influence of the BF cholinergic system on memory function and cortical perfusion. Contract grant sponsor: Deutsche Forschungsgemeinschaft, SCHL 363/4-1.

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Increased susceptibility to flurothyl-induced generalized seizures after immunolesions to cholinergic neurons in the basal forebrain.

Silveira DC, Holmes GL, Schachter SC, Geula C, Schomer DL (1999) Increased susceptibility to flurothyl-induced generalized seizures after immunolesions to cholinergic neurons in the basal forebrain. Neuroscience 1999 Abstracts 643.7. Society for Neuroscience, Miami, FL.

Summary: Intracerebroventricular (icv) injections of toxin 192 IgG-saporin produce almost complete loss of cholinergic neurons in the basal forebrain (BF) with extensive dennervation throughout the neocortex and hippocampus. The association among epilepsy and BF cholinergic neurons, which are involved in learning and memory processes, remains unclear. Intraperitoneal injections of pilocarpine, a cholinergic agonist, elicit seizures. Seizures alter the expression of hippocampal muscarinic receptors in human epilepsy. Immunolesions to BF cholinergic neurons increase the number of generalized seizures induced by rapid amygdaloid kindling. We investigated whether BF cholinergic neurons influence the expression of generalized seizures in model of generalized epilepsy. Adult male rats received icv injections of toxin 192-IgG-saporin (lesioned group) or saline (control group). Following 30 days of icv injections both lesioned and control rats were submitted to flurothyl administration. The latency of onset for the first myoclonic jerk, bilateral forelimb clonus, and tonic seizures were recorded. In addition, the hidden platform version of the Morris water maze was used to assess spatial learning and memory. Brain tissue was processed for acetylcholinesterase activity using sensitive histochemical method. Lesioned rats had significantly (p<0.05) shorter latency of onset of tonic seizures than control rats. Spatial learning and memory was significantly (p<0.05) reduced in lesioned animals compared to controls. These preliminary results indicate that immunolesions to cholinergic neurons in the BF increase the susceptibility to seizures induced by flurothyl. Thus, it appears that BF cholinergic neurons participate in the modulation of generalized seizures in both limbic and generalized epilepsy in rats.

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CTB-saporin induced demyelinating myelopathy in the rat.

Janni G, Lappi DA, Ohara PT, Jasmin L (1999) CTB-saporin induced demyelinating myelopathy in the rat. Neuroscience 1999 Abstracts 731.2. Society for Neuroscience, Miami, FL.

Summary: In designing a rat model of demyelinating disease, we have used a newly developed neurotoxin, the B fragment of cholera toxin (CTB) linked to the potent ribosome inactivating protein saporin. Saporin linked to CTB targets cell expressing ganglioside GM1 on their surface, mainly Schwann cells, oligodendrocytes, and to a lesser degree neurons. After binding to GM1, CTB-Saporin is rapidly endocytosed and induces cell death. We demonstrate that intrathecal injection of 1 µg in 5 µl of CTB-Saporin at the lumbar level produces a demyelinating disease of the spinal cord. Behaviorally, this disease is characterized by an ascending paralysis that progresses most prominently from day 7 to day 14 post-treatment. In approximately half of the animals, the disease progresses to the brainstem, while in the others the disease regresses spontaneously, leaving these animals with only a moderate residual neurologic deficit. Histologically and ultrastructurally, the spinal pathology is characterized by a loss of myelin and oligodendroglyocytes as well as an immune response involving circulating leukocytes. Immunostaining shows the presence of CD8 immunopositive T lymphocytes but not CD4 T lymphocytes. We therefore conclude that CTB-Saporin induced demyelination involves an immune, but not an autoimmune mediated component in addition to the direct cytotoxic effect. Supported by Georgetown University.

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Cholinergic deafferentation of the hippocampus or cortex produces differential modulation of attentional processing.

Waite JJ (1999) Cholinergic deafferentation of the hippocampus or cortex produces differential modulation of attentional processing. Neuroscience 1999 Abstracts 754.4. Society for Neuroscience, Miami, FL.

Summary: Dissociation of attentional changes produced by lesion of the cholinergic neurons in the medial septum (MS) and nucleus basalis magnocellularis (NBM) was investigated by selective lesion with the immunotoxin 192 IgG-saporin followed by testing in the multiple choice serial reaction time task. Male F-344 rats were trained in the 5-choice reaction time task. After criterion performance was attained, the toxin was administered intraparenchymally into the MS (75 ng/site bilateral) and/or NBM (150 ng/site bilateral) to selectively destroy cholinergic neurons projecting to hippocampus and cortex, respectively. Residual ChAT activity, expressed as percent of PBS-infused control, was: in frontal cortex, 28% (NBM); 88% (MS); and 21% (NBM+MS); in hippocampus, 103% (NBM); 18% (MS); and 19% (NBM+ MS). Animals reacquired the baseline task to equivalent levels among groups, based on both accuracy and omissions within ten sessions. MS rats performed with greatest accuracy when the intertrial interval (ITI) was short. They always had fewest omissions. Accuracy for this group suffered when the ITI was long and when a noise was presented just before the light stimulus. NBM rats had the most omissions, but accuracy was generally as good or better than controls and the MS group. Rats with both MS and NBM lesions were frequently between MS and NBM performance curves, putting them close to controls in many tests. They performed worse than all groups in terms of accuracy when the ITI was short and when the light intensity was reduced. Thus, the double lesion had an additive effect when the salience of stimulus was reduced and when the frequency of trials was faster. Supported by NIH NS33371.

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Hippocampal Trk-A receptors are compartmentalized within axonal transport vesicle sites and present in select astrocytes.

Barker-Gibb ML, Einheber S, Milner TA (1999) Hippocampal Trk-A receptors are compartmentalized within axonal transport vesicle sites and present in select astrocytes. Neuroscience 1999 Abstracts 803.6. Society for Neuroscience, Miami, FL.

Summary: Trk-A is a high affinity transmembrane tyrosine kinase receptor which is activated by its ligand, nerve growth factor (NGF), to mediate cell survival and the retrograde transport of NGF by septohippocampal cholinergic neurons. To determine its subcellularlocalization, antibodies to the extracellular domain of the Trk-A receptor (Chemicon; Upstate) were localized immunocytochemically in rat dentate gyrus by light & electron microscopy (LM; EM). These antibodies recognized two bands migrating at -125 and 140 kD on immunoblots of septal and hippocampal lysates. Consistent with previous LM reports, Trk-A-immuno- reactivity (-I) with both antibodies was found in fine, varicose fibers, primarily in the hilus. However, the Chemicon antibody also labeled fibers in the granule and molecular layers (ML) as well as numerous astrocytic profiles in the external and medial zones of the ML and the superficial blade of the hilus. EM analysis of the dentate gyrus using the Chemicon antibody revealed that Trk-A-I was in axons, axon terminals and astrocytes. Trk-A-I in axons was not homogeneous, but was concentrated in patches near regions where vesicles accumulated. Trk-A-I in terminals was affiliated with clusters of small synaptic vesicles frequently located away from synaptic specializations. In both axons and axon terminals, the clusters of Trk-A-labeled vesicles often were adjacent to somatic and dendritic profiles. Trk-A-labeled astrocytes in the hilus regularly closely apposed terminals presynaptic to dendritic spines. The findings support evidence that hippocampal Trk-A receptors are compartmentalized within transport vesicle sites. Also, they suggest that astrocytes play a role in the uptake and retrograde transport of NGF by septohippocampal cholinergic neurons to support their survival. (Support: MH42834; DA 08259)

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Selective cholinergic lesions of the horizontal limb of the diagonal band of Broca affect odor perception in rats.

Garcia P, Linster C, Hasselmo ME, Baxter MG (1999) Selective cholinergic lesions of the horizontal limb of the diagonal band of Broca affect odor perception in rats. Neuroscience 1999 Abstracts 559.2. Society for Neuroscience, Miami, FL.

Summary: We have recently shown, in behavioral experiments with rats, that perceptual similarities between aliphatic aldehydes can be at least partially predicted from the neural responses in the olfactory bulb (Linster and Hasselmo, Physiol. Behav., in press). These experiments showed that an overlap in neural responses to "similar" odorants, as seen in the olfactory bulb (Imamura et al., J. Neurophysiol. 68: 1986, 1992), is predictive of a greater perceptual similarity of these odorants in a behavioral task. Computational models of the olfactory bulb (OB) predict that cholinergic input to the olfactory bulb arising from the horizontal limb of the diagonal band of Broca (HDB) modulates the neural representation of odorants in rats (Linster and Hasselmo, Behav. Brain. Res., 84:117, 1997), possibly leading to a change in perceptual similarity as measured by the behavioral response. We now report a behavioral test of these predictions. The cholinergic neurons of the HDB were lesioned using the specific cholinergic toxin 192 IgG-saporin. Two groups of male Sprague-Dawley rats (10 lesioned and 8 sham-operated rats) were trained to retrieve a reward from a cup filled with bedding covering a cotton swab saturated with odorant. We trained rats on a series of six aliphatic aldehydes and tested generalization between all pairs of odorants as well as with a control odor (n-amyl-acetate). Generalization was quantified as the amount of time spent digging in response to a test odor compared to the response to the conditioned odor (in the absence of reward). Our behavioral paradigm showed no difference between the two groups in the response to the conditioned or control odors. However, the two groups differed significantly in response to the test odors. Although sham-operated rats did not generalize to aldehydes differing by more than 2 carbons from the trained odor, lesioned rats generalized to all aldehydes tested. This work was supported by NSF grant IBN-9723947.

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Selective lesions of the nucleus basalis magnocellularis in rats do not affect simple association learning.

Butt AE, Bowman TD, Novotnev JS, Rogers JL, Tanabi A (1999) Selective lesions of the nucleus basalis magnocellularis in rats do not affect simple association learning. Neuroscience 1999 Abstracts 559.4. Society for Neuroscience, Miami, FL.

Summary: We have previously argued that damage to the cholinergic nucleus basalis magnocellularis (NBM) selectively impairs complex or configural association learning while sparing simple association learning (Butt & Hodge, 1997; Butt et al., 1998, Soc. Neurosci. Abst.). However, contrary to our hypothesis, in an earlier study using the less selective neurotoxin quisqualic acid, we found that simple association learning was moderately impaired in NBM-lesioned rats (see Butt & Hodge, 1997). It remained unclear whether the observed behavioral impairment in that study was due to loss of cholinergic input to neocortex or was instead due to non-specific damage to other brain structures. In the current study, therefore, we used the highly selective immunotoxin Ig-G saporin to create bilateral lesions of the NBM in male Long-Evans rats (350 g) and then tested these rats in a simple association learning paradigm. NBM lesioned rats (n = 4) and sham-operated rats (n = 6) underwent 20 consecutive days of training in a simple operant discrimination between a food-reinforced tone (T+) and a non- reinforced light (L-). Results showed that performance in NBM-lesioned rats was normal in all respects; both groups acquired the task, committing progressively greater numbers of successful responses to T+ and progressively fewer responses to L-, as well as diminishing the number of (non-reinforced) responses committed during the inter-trial interval. The hypothesis that NBM lesions spare simple association learning was thus supported. Despite the absence of impairment in this simple association task, we maintain that the NBM is involved in complex or configural association learning as demonstrated in separate experiments (see Butt et al., 1998, Soc. Neurosci. Abst.). (Supported by a University Research Committee Grant awarded to A. E. Butt by the Indiana State University Office of Sponsored Programs).

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Lack of effect of intraventricular OX7-saporin on working memory in the rat.

Wrenn CC, Lappi DA, Wiley RG (1999) Lack of effect of intraventricular OX7-saporin on working memory in the rat. Neuroscience 1999 Abstracts 559.5. Society for Neuroscience, Miami, FL.

Summary: The immunotoxin 192 IgG-saporin (192-sap) has been shown by our laboratory and others to be a highly selective agent for the production of lesions of the rat cholinergic basal forebrain(CBF). Such lesions can be produced by either intraventricular (i.c.v.) or intraparenchymal injection of the immunotoxin and can result in cognitive deficits. One potential shortcoming of i.c.v. injection of 192-sap is that it kills cerebellar Purkinje cells in addition to killing the neurons of the CBF. Thus, it is unclear whether or not cognitive deficits that arise after i.c.v. 192-sap are due to loss of the CBF or loss of Purkinje cells. We addressed this problem by injecting rats i.c.v. with saline, 2 µg 192-sap, 4 µg 192-sap, or 1 µg OX7-saporin(OX7-sap). OX7-sap is an immunotoxin shown by our laboratory to selectively lesion Purkinje cells after i.c.v. injection. The 1 µg dose was chosen based on pilot anatomical work which showed this dose to produce Purkinje cell loss of similar pattern and extent to that produced by 4 µg of 192-sap. These rats were tested in a radial maze working memory paradigm, and it was found that the 4 µg 192-sap group made significantly more working memory errors than either the saline or OX7-sap injected groups. These data suggest that Purkinje cell loss alone is not sufficient to disrupt cognitive processes. (Supported by Departmento f Veterans Affairs and the Vanderbilt Center for Molecular Neuroscience).

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A developmental role of the cholinergic basal forebrain: behavioural and neurochemical effects of neonatal 192 IgG-saporin lesions.

Ricceri L, Calamandrei G, Berger-Sweeney J (1999) A developmental role of the cholinergic basal forebrain: behavioural and neurochemical effects of neonatal 192 IgG-saporin lesions. Neuroscience 1999 Abstracts 559.6. Society for Neuroscience, Miami, FL.

Summary: Cholinergic basal forebrain (BF) fibers begin to innervate neocortex and hippocampus during the first week of life in rodents. Because this is a dynamic period in cortical synaptogenesis and organization, we have hypothesized that the cholinergic BF provides its targets with critical signals that influence cortical organization and cognitive behavioral later in life. Neocortical projection fibers reportedly innervate their targets early in the first postnatal week, whereas hippocampal projections innervate their targets later in the first postnatal week. Previously we have shown that intraventricular injections of the selective cholinergic immunotoxin 192 IgG saporin on postnatal day (pnd) 7 impair passive avoidance (PA) acquisition, but not retention, on pnd 15-16 and significantly reduce hippocampal (78%) and neocortical (64%) choline acetyltransferase (ChAT) activity. In the present study, we attempted to produce significant reductions in cholinergic activity earlier in development, when primarily neocortical projections are developing, and assess effects on neurochemistry and behavior. Wistar rats received intraventricular injections of 192 IgG saporin on pnd 1 and 3. PA acquisition and retention were assessed on pnd 15-16. Lesioned rats acquired the PA task slower than control littermates, whereas 24-hr retention was not affected. On pnd 20, ChAT activity in neocortex and hippocampus was assessed. There was a 63% reduction in neocortical and 45 % reduction in hippocampal ChAT activity. These data suggest that interrupting cholinergic input to neocortex and hippocampus early in the first week of life affects cognitive behaviors. Interestingly, this early lesion also leads to abnormalities in cortical cytoarchitecture that strongly resemble those occurring in developmental disorders associated with mental retardation (Robertson et al. 1998). Supported by ISS intramural fundings,NSF IBN9458101 and Whitehall Foundation.

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GABAergic septohippocampal neurons are not necessary for spatial memory. (Poster)

Secor A, Nocera R, Pang KCH (1999) GABAergic septohippocampal neurons are not necessary for spatial memory. (Poster). Neuroscience 1999 Abstracts 559.9 . Society for Neuroscience, Miami, FL.

Summary: The medial septum/diagonal band of Broca (MS-DB) provides a major input to the hippocampus, and nonselective lesions of MS-DB neurons or their projections to the hippocampus impair spatial memory on several tasks. Two MS-DB cell types project to the hippocampus, the cholinergic and GABAergic neurons. Performance on several spatial memory tasks is less severely affected by selective lesions of the cholinergic MS-DB neurons with 192-IgG saporin (SAP) than by nonselective MS-DB lesions. These results indicate a possible important role of GABAergic septohippocampal (SH) neurons in spatial memory. The present study examined the importance of the GABA SH neurons in spatial memory. GABA SH neurons were destroyed by kainic acid (KA) administration to the MS-DB. Female Sprague- Dawley rats were treated with saline, KA, 192-IgG saporin (SAP) or a combination of both (KA/SAP). After a two-week recovery period, rats were tested on an 8-arm radial maze and a water maze. Immunocytochemistry was performed to verify the lesions. KA (1 µg/µll) produced a nearly complete lesion of parvalbumin immunoreative GABA SH neurons. This dose of KA did not significantly reduce the number of cholinergic neurons. SAP eliminated all cholinergic neurons and the combination KA/SAP produced general degeneration and tissue shrinkage not seen following KA or SAP alone. Acquisition of the 8-arm radial maze task and performance of a delay version of the task were not altered by KA alone or SAP alone, but were significantly impaired by KA/SAP. Acquisition of the water maze task was not significantly affected by KA, but was slightly impaired by SAP and severely impaired by KA/SAP. These results demonstrate that GABA SH neurons are not necessary for spatial memory. The possible interaction between GABA and cholinergic SH neurons will be explored. Supported by NS35389 and AG16093.

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Selective immunolesion of substance P receptor expressing interneurons in the hippocampus.

Borhegyi ZS, Wiley RG, Lappi DA, Morrell J, Buzsáki G (1999) Selective immunolesion of substance P receptor expressing interneurons in the hippocampus. Neuroscience 1999 Abstracts 561.15. Society for Neuroscience, Miami, FL.

Summary: A ribosome inactivating protein, saporin, conjugated to substance P (SP-SAP) was used to selectively damage substance P receptor expressing interneurons in the dentate gyrus of the rat hippocampus. Three different doses (50ng, 25ng and 5ng) were tested in animals surviving 1, 2, 3, 5 and 10 weeks. Immunohistochemistry (parvalbumin, calbindin, calretinin, SPR, GluR2 and mGluRl1α) was carried out to examine specific or non-specific damage. The results were examined at light and electronmicroscopic level. The highest (50ng) dose eliminated SPR elements in an approximately 3mm area, but it also caused nonspecific damage around the center. In rats injected with 5ng nonspecific damage to granule cells and mossy cells was not observed and SPR interneurons were selectively eliminated a far as 0.7mm from the center of the injection. The loss of SPR immunoreactive cells was clearly visible after two weeks. The selective lesion of a well-defined subgroup of hippocampal interneurons can reveal their physiological role in normal function. Furthermore, the permament and selective absence of interneurons may be an effective tool for creating focal epilepsy. This work was supported by NIH, NIMH and Eötvös fellowship.

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

Effects of cortical cholinergic deafferentation upon processing capacity as assessed by an olfactory span task in rats.

Sarter M, Turchi J, Gonzalez K (1999) Effects of cortical cholinergic deafferentation upon processing capacity as assessed by an olfactory span task in rats. Neuroscience 1999 Abstracts 554.6. Society for Neuroscience, Miami, FL.

Summary: Cortical cholinergic deafferentation, produced by infusions of 192 IgG-saporin into the basal forebrain of rats, results in impairments of processing capacity as measured by performance in a divided attention task (Turchi & Sarter, 1997). In the present experiment, processing capacity was assessed in rats by employing two versions of an olfactory span task (adapted from Dudchenko, Wood, Faherty & Eichenbaum 1998): match-to-sample (MTS) and non-match-to-sample (NMTS) olfactory discrimination paradigms involving multiple spices (dill, clove, etc.) as stimuli. Subjects for the MTS group were initially trained to select the sample-spice whereas subjects for the NMTS group were trained to identify the novel spice presented together with the sample-spice. After animals acquired the matching and non-matching rules, a steadily increasing number of spices were presented in randomized sequence configurations for successive trials within a daily test session, and the olfactory span of the animal was defined as the number of correct responses generated before the first error. Once the rats attained a stable performance criterion (average pre-lesion span: 16.4 ± 0.2), animals received basal forebrain infusions of 192 IgG-saporin. The results indicate that the lesion impaired NMTS rats performance following an intertrial delay insertion between trials. This experiment provides additional evidence implicating the cholinergic system in the mediation of processing capacity. Supported by NIH Grants NS32938, NS37026 and AG10173.

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Inhibition of mustard oil-induced thermal hyperalgesia in an operant escape task by substance P-saporin.

Wiley RG, Lappi DA, Vierck CJ (1999) Inhibition of mustard oil-induced thermal hyperalgesia in an operant escape task by substance P-saporin. Neuroscience 1999 Abstracts 271.1. Society for Neuroscience, Miami, FL.

Summary: Substance P (SP) armed with the ribosome inactivating protein, saporin (SAP), selectively destroys neurons expressing the NK-1 receptor, attenuates withdrawal responses after capsaicin injection, after a Chung lesion or CFA and blocks phase 2 of the formalin test. These tests rely on innate “reflex” behaviors (withdrawal or licking) and the primary effects were to mechanical stimuli. In the present study, we sought to determine the effects of lumbar i.t. SP-SAP on reflexes and operant escape responses to thermal stimuli. Rats received lumbar i.t. injections of 175 ng SP-SAP (N=7), 25 ng of [Sar8MetOH11]-SP-SAP (N=8) or PBS with 1 mg/ml BSA (N=8). Nine rats served as naive controls. After recovery from surgery, all rats were adapted to thermal reflex testing and separately trained to escape to a brightly lit room temperature shelf from a dark surface at 47°C, 44°C and 0.3°C. There were no differences between groups at baseline on the escape task or reflex tests at any of the 3 temperatures. When tested at 44°C 3 hours after application of mustard oil to the dorsal surface of both hindpaws, controls spent significantly more time on the escape shelf whereas SP-SAP treated rats did not. In contrast, when tested 3 hrs after mustard oil at 44°C, all rats showed similar reflex responses with decreased latency to licking, more licking and guarding. These results indicate that the SP-SAP lesion of lamina I neurons expressing NK-1 receptor in the spinal dorsal horn prevents enhanced operant escape behavior, but not enhanced reflex responses. That is, the aversive quality of mustard oil-induced thermal hyperalgesia was blocked without interfering with nocifensive reflexes. Also, the anti-hyperalgesia effects ofl umbar intrathecal SP-sap include thermal hyperalgesia. This approach may prove valuable in the treatment of chronic, intractable pain. (This work supported by the NIH and the Department of Veterans Affairs).

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

Depletion of IB4-binding sensory neurons results in elevated nociceptive thresholds.

Vulchanova L, Stone LS, Olson T, Riedl MS, Elde R, Honda CN (1999) Depletion of IB4-binding sensory neurons results in elevated nociceptive thresholds. Neuroscience 1999 Abstracts 272.8. Society for Neuroscience, Miami, FL.

Summary: The lectin IB4 binds to and is specifically taken up by a subset of small sensory neurons, proposed to play a role in nociception. To examine the role of these neurons in sensory transmission we used a conjugate of IB4 and the toxin saporin (IB4-sap). IB4-sap (2 µg/5 µl) was injected in the left sciatic nerve of rats. Three days after the injection, the conjugate was visualized in the left L4 and L5 DRG using antisera to either the lectin or saporin. The cells labeled by these antisera were not stained by the Nissl-like marker ethidium bromide, suggesting disruption of their protein synthesis. Twenty one days after the injection there was a 36% reduction in the total number of neurons and a 50% reduction in IB4-binding neurons in L5 DRG of IB4-sap injected rats. Moreover, in dorsal horn of spinal cord, the projection site of the left sciatic nerve was devoid of IB4 binding. P2X3 immunostaining was also dramatically reduced, while the decrease in staining for SP, CGRP and VR1 was less pronounced. The responsiveness of the IB4-sap treated rats to noxious thermal and mechanical stimuli was examined using radiant heat and von Frey filaments, respectively. There was a significant increase in the withdrawal latency to thermal stimuli at day 10 and the withdrawal threshold to mechanical stimuli at day 14 post-treatment. By day 21 both the thermal and mechanical thresholds returned to baseline levels. We have shown that depletion of IB4-binding sensory neurons results in transient elevation of nociceptive thresholds. These findings suggest that IB4-binding neurons mediate the signaling of noxious stimuli and that an efficient compensatory mechanism appears to be activated within days of their loss. Supported by NIH grants DA09641 and DE07288.

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NGF-mediated alteration of NF-κB binding activity after partial immuno-lesions to rat cholinergic basal forebrain neurons.

Gu Z, Toliver-Kinsky T, Glasgow J, Cain L, Perez-Polo JR (1999) NGF-mediated alteration of NF-κB binding activity after partial immuno-lesions to rat cholinergic basal forebrain neurons. Neuroscience 1999 Abstracts 300.15. Society for Neuroscience, Miami, FL.

Summary: Memory loss and cognitive deficits in die aged and in patients with Alzheimer’s disease (AD) are often associated with cholinergic deficits within the NGF-dependent cholinergic basal forebrain neurons (CBFNs) that project to the cortex, hippocampus, and olfactory bulb. Although the causes of these cholinergic deficits are not fully understood, the increases in activity of the transcription factor NF-κB in the brains from aged and AD patient may reflect chronic transcription enhancement of stress response genes that affect cholinergic expression and neuronal death. In order to ascertain whether endogenous NGF effects on ChAT and NF-κB may account for recovery from stress, a partial immunolesion (PIL) to CBFNs, which is produced by the injection of 192 IgG-saporin, an immunotoxin selectively taken up by low-affinity NGF receptor p75NTR-bearing neurons, was conducted and followed by infusion of anti-NGF. Both PIL and anti-NGF treatment decreased ChAT activity in cortex, hippocampus, and olfactory bulb. NGF protein levels increased significantly in the olfactory bulb, but not the cortex or hippocampus after PIL treatment. Infusion of anti-NGF abolished the PIL-induced NGF increases in cerebrospinal fluid. We also found that NF-κB binding activity to both the κ light chain enhancer and the ChAT promoter specific consensus sequence increased in PIL-induced cortex but not hippocampus after anti-NGF infusion as measured by electrophoretic mobility shift assays (EMSAs). This is consistent with the hypothesis that NF-κB contributes as a repressor to the transcriptional regulation of ChAT by NGF. Taken together with reports of increased levels of NF-κB activity in brains of aged rats and of AD patients, it is likely that NGF-mediated changes in NF-κB activity in part reflect responses to age-associated cholinergic deficits. (Supported in part by NINDS Grant NS 33288)

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Lesions of basal forebrain cholinergic neurons eliminate the modulatory effects of benzodiazepine receptor ligands on behavioral and cardiovascular reactions in an anxiogenic paradigm.

Stowell JR, Bemtson GG, Sarter M (1999) Lesions of basal forebrain cholinergic neurons eliminate the modulatory effects of benzodiazepine receptor ligands on behavioral and cardiovascular reactions in an anxiogenic paradigm. Neuroscience 1999 Abstracts 358.5. Society for Neuroscience, Miami, FL.

Summary: We have previously shown that basal forebrain cortical cholinergic projections mediate potentiation of the cardiovascular defensive response by the putative anxiogenic benzodiazepine receptor partial inverse agonist FG 7142 (Bertnson et al., 1998). The present study assessed the effects of lesions of the basal forebrain cholinergic neurons on operant responding in a conditioned suppression paradigm and the modulating effects of benzodiazepine receptor (BZR) ligands in this paradigm. Nine animals received basal forebrain infusions (0.18 µg/hemisphere) of the immunotoxin 192 IgG-saporin. Lesioned and control (n=9) animals were trained in a conditioned suppression paradigm using a tone for the conditioned stimulus (CS) and a rear panel light for a contextual cue. FG 7142 (8 mg/kg), chlordiazepoxide (CDP, 8 mg/kg), and vehicle were administered i.p. in subsequent extinction sessions. In control animals, operant responding was suppressed during presentation of the CS and contextual cue. The BZR partial inverse agonist FG 7142 exaggerated this suppression,while CDP attenuated it. Lesioned animals were less suppressed than controls across stimulus conditions, with the largest difference between groups observed during presentation of the contextual cue. Presentation of the contextual cue was also associated with a cardioacceleratory response in control animals, and this response was significantly attenuated in lesioned animals. Furthermore, the modulatory effects of BZR ligands on behavioral and autonomic reactions observed in control animals were eliminated in lesioned animals. These data support an important role for cholinergic basal forebrain neurons in the behavioral and autonomic response to anxiety. Funded by HL54428.

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