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Residual hippocampal cholinergic functions after 192 IgG-saporin lesions of the medial septum/ventral diagonal band (MS/VDB)

Chang Q, Gold PE (2002) Residual hippocampal cholinergic functions after 192 IgG-saporin lesions of the medial septum/ventral diagonal band (MS/VDB). Neuroscience 2002 Abstracts 82.8. Society for Neuroscience, Orlando, FL.

Summary: 192 IgG-saporin (SAP) injections into the MS/VDB reportedly destroy acetylcholine (ACh) neurons projecting to hippocampus (HC) without associated impairments of learning and memory on HC-dependent tasks. These findings contrast sharply with those obtained with many other methods showing close associations between ACh functions in the HC and learning and memory. The present experiment addressed this conflict. SAP was injected into MS/VDB 1 week before the start of neural and behavioral measures. We found: 1) Using in vivo microdialysis, release of ACh in the HC was not abolished but was ~30% of control values. The percent increase in ACh release during spontaneous alternation testing was greater in SAP-treated than in control rats. 2) SAP-treated rats had significant impairments on the HC-dependent alternation task. Moreover, intra-HC injections of physostigmine (20 ng in 1 ┬Ál), an indirect ACh agonist, enhanced alternation scores. 3) Physostigmine (0.6 mg/kg, IP) induced more intense tremors in SAP-treated than in control rats. 4) While SAP-treated rats had near-total depletion of cells in MS/VDB stained using immunocytochemistry for choline acetyltransferase (ChAT), quantitative densitometry showed no depletion of ChAT staining in either CA1 or the dentate gyrus in the SAP group. These findings suggest that there are residual and even heightened ACh functions which can compensate for the insult of MS/VDB SAP lesions, complicating the use of this lesion to evaluate the role of septohippocampal cholinergic projections in learning, memory or other functions.

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

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