The role of the anterior hypothalamus in affective defense behavior elicited from the ventromedial hypothalamus of the cat

Abstract

In the preceding paper a hypothalamic circuit subserving feline affective defense behavior was described. This circuit included an ascending component from the ventromedial nucleus to the anterior hypothalamus and a descending component from the anterior hypothalamus to the midbrain central gray substance. The present study was undertaken to test the hypothesis that the anterior hypothalamus plays a central role in the organization of this functional pathway. In the first part of this study, dual stimulation methods were utilized to demonstrate that concurrent stimulation of the ventromedial hypothalamus facilitates the occurrence of affective defense responses elicited from the anterior hypothalamus. In the second part of the study, lesions placed in the anterior hypothalamus significantly increased the latency and threshold current for affective defense responses elicited from the ventromedial hypothalamus. [ 14C]2-deoxyglucose autoradiography confirmed tha fact that anterior hypothalamic lesions effective in blocking affective defense were placed in regoins where the vast majority of ventromedial hypothalamic fibers terminate. In contrat, lesions which had little or no effect upon the latency or threshold for affective defense elicited from the ventromedial hypothalamus appeared to leave intact the connections from the ventromedial to the anterior hypothalamus. These findings are consistent with the proposed intrahypothalamic anatomical substrate subserving affective defense behavior described in the preceding paper.