INVOLVEMENT OF SEPTAL MUSCARINIC RECEPTORS IN CHOLINERGICALLY MEDIATED CHANGES IN RAT REARING ACTIVITY

We tested the hypothesis that septal muscarinic receptors of the rat a re involved in exploratory behavior control, at least as reflected in the measure of rearing activity. At a dose capable of inducing hippoca mpal theta rhythm, carbachol injection into the septum significantly i ncreased the number of rearings from the 2nd to the 5th min postinject ion. The increase was maximal in the 3rd min and gradually declined un til the 9th min postinjection, when it was near the control level. Thi s behavioral effect was blocked by prior injection of atropine. These data, when considered with other findings showing a similar motor resp onse caused by the hippocampal injection of the cholinergic agonist, s trongly suggest that the cholinoceptive cholinergic components of the septohippocampal system play a role in the release of exploratory beha vior. This role might be mediated via muscarinic receptors at the sept al level. Moreover, the time course of behavioral action of carbachol injected into the septum is of particular importance for studies on th e effect of the drug on performance of the rat in learning and memory tests requiring contribution of exploratory behavior. (C) 1997 Elsevie r Science Inc.