sfn1999

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.

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

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.

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

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.

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

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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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. PMID: 0

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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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.

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

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.

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

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).

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

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).

Related Products: 192-IgG-SAP (Cat. #IT-01), OX7-SAP (Cat. #IT-02)

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.

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