Septohippocampal cholinergic changes after destruction of the A10-septal dopaminergic pathways.
Mice were injected bilaterally into the septum with 6-hydroxydopamine and 6 weeks later the hippocampi were assayed for activity of choline acetyltransferase, muscarinic receptor binding capabilities and for formation of inositol phosphate in response to direct (carbachol) or presynaptically elicited (K+) stimulation of the postsynaptic receptors. Levels of dopamine in the septum were reduced by 70% in the lesioned animals and hippocampal choline acetyltransferase was elevated by the same amount. The Bmax of muscarinic binding was significantly reduced without changes in Kd; nevertheless, carbachol-induced stimulation of formation of inositol phosphate was unaffected. The response to K+ was markedly elevated in the 6-hydroxydopamine-treated animals. Thus, the regulatory effect of A10-septal dopaminergic pathways on the septohippocampal cholinergic innervations is both on the presynaptic and postsynaptic levels.
Yanai, J; Rogel-Fuchs, Y; Pick, CG; Slotkin, T; Seidler, FJ; Zahalka, EA; Newman, ME
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