CHANGES IN BRAIN MUSCARINIC ACETYLCHOLINE RECEPTORS AND BEHAVIORAL-RESPONSES TO ATROPINE AND APOMORPHINE IN CHRONIC ATROPINE-TREATED RATS

Chronic blockade of cholinergic transmission with atropine resulted in a decrease in atropine-induced activity in the rats, whereas apomorphine - induced locomotion was enhanced. Maximal binding of 3H-quinuclidinyl benzilate (QNB), a muscarinic antagonist, to homogenate of cerebral cortex, striatum and hippocampus was significantly higher in chronic atropine-treated rats than in control animals. No difference was observed in KD value of the specific 3H-QNB binding or in ID50 value of oxotremorine in inhibiting 3H-QNB binding. No change in the specific binding of 3H-spiroperidol, a dopaminergic antagonist, was observed in those three regions of brains of chronic atropine-treated rats when it was compared with that of control animals. The role of brain muscarinic acetylcholine receptors in behavioral responses is discussed relating an effect of dopaminergic neurons on cholinergic activities. © 1979.