Evidence for involvement of endogenous acetylcholine in emotional-aversive response in the cat

Abstract

1. The purpose of the present study was to provide evidence for involvement of endogenous acetylcholine in naturally as well as pharmacologically induced emotional behaviour in the cat. 2. Emotional-aversive responses of 10 cats were naturally evoked by presentation of a dog or the responses were pharmacologically induced by intracerebral injections of cholinomimetics. 3. Naturally evoked emotional behaviour was abolished by i.p. pretreatment with atropine sulfate (1 mg/kg), but not by atropine methyl nitrate, or it was significantly decreased by bilateral intracerebral injection of atropine sulfate (5 micrograms/microliter). 4. On the other hand, intracerebral injections of physostigmine (100 micrograms/microliter), an acetylcholinesterase inhibitor which elevates the level of endogenous acetylcholine, induced the fully developed emotional-aversive response comparable with natural behaviour and with responses induced by carbachol (10 micrograms/microliter). 5. The results demonstrate that the endogenous acetylcholine in the basal forebrain and diencephalic areas play a role in naturally occurring emotional aversive behaviour in cats.