The principal objective of this work was to investigate the possibility that the effects of a number of drugs on conditioned avoidance behaviour of the laboratory rat, could be attributed to an action(s) on the functioning of catecholamine-containing neurons of the amygdala. In order to restrict drug action to the amygdala, a cannula-guide system was prepared and fixed to the skull of the experimental animal prior to behavioural observation. Drug solutions were injected into the vicinity of the nucleus amygdaloideus centralis in conscious, unrestrained rats, through an injection cannula passed down the guide tube. The effects of drugs administered by this route on the acquisition of the pole-climb conditioned avoidance response were observed. Low doses of d-amphetamine, apomorphine and benztropine applied to the amygdala, resulted in facilitated acquisition of the conditioned response over the five days of training. Higher doses disrupted this behaviour. Haloperidol and pimozide, two competitive antagonists of dopamine, and desmethylimipramine, a potent blocker of noradrenaline re-uptake, decreased the rate of acquisition of the conditioned response. The disruptive effects of the high dose of d-amphetamine and of desmethyl-imipramine were reversed by the alpha-adrenoreceptor blocking drug phentolamine. Application of dopamine and noradrenaline increased and decreased respectively, the rate of acquisition of the conditioned response. The results are discussed in relation to the proposed mechanism of action of these drugs at the synapse and how they might modify nervous activity. Proposals have been made regarding the functional significance of catecholamine-containing neuron systems of the amygdala in conditioned avoidance behaviour. Suggestions for further research have also been made.
|Date of Award||1977|