Functional relationship of lateral hypothalamus and amygdala in control of eating

Cannulas were stereotactically implanted in the lateral hypothalamus and the ipsilateral amygdaloid cortical nucleus of 7 male albino rats, Wistar strain. After functional checking of the accuracy of implants by adrenergic elicitation of increased food intake, the animals were injected with combinations of noradrenaline, phenoxybenzamine or tolazoline, or placebo under 6 treatment conditions, while food-and water satiated. The elicitation of increased food intake in the satiated rat by adrenergic stimulation of the lateral hypothalamus was confirmed, and it was further found that simultaneous adrenergic stimulation of the amygdaloid cortical nucleus augmented this increase. However, simultaneous anti-adrenergic blockade in the amygdaloid cortical nucleus reduced eating to control level. The lack of response of the amygdaloid cortical nucleus to adrenergic stimulation in the satiated rat, under simultaneous stimulation of the lateral hypothalamus with either placebo or an adrenergic blocker, was also demonstrated. It was concluded that the amygdaloid cortical nucleus has a modulatory influence on eating behavior, which is dependent on the level of activity in the lateral hypothalamus, and further that this modulatory influence is necessary to the behavioral output of the hypothalamic system. This is the same relationship between the hypothalamus and amygdala previously demonstrated in regard to drinking behavior and these results are seen as supporting the behavioral generality of the functional relationships reported.