sfn1999

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.

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

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)

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)

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

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)

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)

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.

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