Needles for the local micro-injection of neurotransmitters were permanently implanted into the amygdaloid complex in 36 cats. In the free behaviour situation the micro-injection of serotonin (5-HT) into the amygdala elicited an attention response, an exploratory-motor reaction and salivation. In addition to these the micro-injection of aeetyleholine (ACH) elicited emotional reactions (aggressiveness), the seizure activity and also behavioural inhibition and sleep. The micro-injections of noradrenaline elicited no reactions.
The pretreatment with imipramine inhibited the activation of behaviour, emotional reactions, seizures and salivation produced by the micro-injection of ACH into the amygdala. The activation of behaviour and salivation was also inhibited by promazine. Benaetyzine suppressed the salivation induced by ACH. Imipramine, promazine and benactyzine influenced the activation of behaviour produced by the micro-injection of 5-HT into the amygdala in different ways: imipramine and promazine decreased this activation but benactyzine did not. The salivation elicited by 5-HT was markedly enhanced by imipramine. After pretreatment with imipramine (but not with benactyzine and promazine) 5-HT produced vomiting. A possible role for the antagonism of imipramine to ACH and its synergism with 5-HT is discussed in relation to mode of its antidepressant action.