Hippocampal distribution of acetylcholine, muscarinic receptors and cyclic GMP.

Abstract The regional distribution of acetylcholine (ACh), guanosine 3′,5′-monophosphate (cyclic GMP), ACh fractional rate constant, ACh turnover rate and [ 3 H]-quinuclidinyl benzilate (QNB) binding were measured in various regions of the rat hippocampus. In coronal sections of the hippocampus, concentrations of both ACh and cyclic GMP were found to be the highest in sections at the amygdaloid end. Within subsectional areas of coronal sections of the hippocampus (CA-1, CA-3, and dentate gyrus). the cyclic GMP content and the affinity of [ 3 H]-QNB specific binding sites were the highest in the CA-3 and dentate gyrus regions, while the density of [ 3 H]-QNB specific binding was the highest in the CA-1 area. In contrast, the ACh turnover rate was higher in the CA-3 area than in dentate gyrus or CA-1 area. This study demonstrates that an increase of ACh utilization, [ 3 H]-QNB binding sites and cyclic GMP content appears to occur in some specific areas of the hippocampus. These findings suggest that the dissection described in the present experiments is useful in the study of cholinergic regulation of cyclic GMP content of some regions of the hippocampus.