Participation of the Central Amygdaloid Nucleus in the Response of Adrenocorticotropin Secretion to Immobilization Stress: Opposing Roles of the Noradrenergic and Dopaminergic Systems

Abstract

Bilateral lesions of the amygdaloid central nucleus (ACE) significantly diminished the secretion of ACTH in response to immobilization stress. Stress is associated with increased noradrenergic activity in the ACE and in the anterior and lateral hypothalamic areas. In comparison with intact stressed animals, lesion of the ACE reduced the noradrenergic activity in response to stress within the anterior and lateral hypothalamic areas, the arcuate and paraventricular nuclei of the hypothalamus and the bed nucleus of the stria terminalis. These results support the hypothesis of a stimulatory role for the noradrenergic system in the ACE on ACTH secretion. Stress decreased dopaminergic activity in the ACE, the cortical nucleus of the amygdala, the dorsomedial and ventromedial nuclei of the hypothalamus and the ventral tegmental area. In comparison with intact stressed rats, lesion of the ACE reduced dopaminergic activity in the anterior and lateral hypothalamic areas. Our results support the hypothesis of an inhibitory role of the dopaminergic system, particularly in the ACE, on ACTH secretion. This study also indicates that, in the control of ACTH secretion in response to immobilization stress, the noradrenergic and dopaminergic systems act in opposition to one another in certain brain structures such as the anterior and lateral hypothalamic areas and the ACE.