Contribution of cholinergic and gabaergic functions to memory processes inBALB/cANnCrlBR mice

Several lines of evidence indicate that glucose influences on memory depend on interactions between glucose, glucoregulation and hippocampal cholinerg ic function. We previously demonstrated that glucose and scopolamine differ entially affected memory consolidation for an operant bar pressing task in two closely-related BALB/c mouse strains. Whereas glucose normally improves memory in several animal strains, memory consolidation was not effected by systemic glucose injections in BALB/cANnCrlBR mice. Moreover, these mice w ere relatively insensitive to the normally observed amnestic effects of sco polamine. We therefore sought to determine whether cholinergic mechanisms i n the dorsal hippocampus were involved in such atypical drug effects on mem ory processing in that strain of mice. In Experiment 1, we examined whether post-training oxotremorine would also atypically influence memory consolid ation for an appetitively reinforced operant bar pressing task following mi croinjection in the dorsal hippocampus. In Experiment 2, we examined the ef fects of intrahippocampal GABA(A) drugs on memory consolidation. The non-se lective muscarinic agonist, oxotremorine, dose-dependently impaired memory and the GABA(A) antagonist, bicuculline, improved retention in BALB/cANnCrl BR mice. It was concluded that GABA-mediated influences on hippocampal pyra midal output in BALB/cANnCrlBR mice and other strains are similar; but the amnestic effects of oxotremorine from the dorsal hippocampus were opposite to facilitating effects normally observed in other animal strains. Results are discussed relative to possible altered septo-hippocampal cholinergic ne urotransmission in BALB/cANnCrlBR mice. (C) 1999 Elsevier Science B.V. All rights reserved.