[Effect of monoamines microinjected into the amygdaloid nucleus on the lateral hypothalamic self-stimulation...

The effect of serotonin and noradrenaline injections in the amygdalar nuclei on the reaction of self-stimulation of the lateral hypothalamus was studied in rats. The increase of exogenous serotonin level in the amygdala phasically intensified the self-stimulation and activated emotionally negative forms of behaviour. The increase of noradrenaline content phasically lowered the frequency of self-stimulation and evoked emotionally positive forms of behaviour which did not depend on the lateral hypothalamus stimulation. It is supposed that the amygdala takes part in the mechanism of sensory reinforcement connected with learning and being in definite relations with the centres of positive reinforcement of the lateral hypothalamus, while amygdalar monoamines form the neurochemical basis for the control of the reinforcing properties of external stimuli.