Norepinephrine depletion in the amygdala inhibits CRF-41, ACTH, and corticosterone responses following photic simulation.

The effects of amygdaloid norepinephrine depletion by 6-hydroxydopamine on changes in corticotropin releasing factor-41 (CRF-41) and serum adrenocorticotropic hormone (ACTH) and corticosterone levels, following neural stimuli were investigated. In intact animals, photic or acoustic stimulation caused CRF-41 depletion from the median eminence and a rise in serum ACTH and corticosterone levels. In rats with amygdalar norepinephrine depletion there were no changes in basal CRF-41, ACTH, or corticosterone levels. However, the above responses of the hypothalamo-pituitary adrenocortical axis were blocked following photic, but not acoustic, stimulation. These results indicate that the facilitatory role of the amygdala on the above responses following photic stimulation depends on the presence of norepinephrine in this region.