A comparison of the pituitary adrenal activity elicited by electrical stimulation of preoptic, amygdaloid and hypothalamic sites in the rat brain.

Abstract

In rats anesthetized with pentobarbital, increments in corticosterone concentration were elicited upon electrical stimulation through chronically implanted electrodes. Prestimulation steroid levels were low. Poststimulation levels varied according to the site stimulated. These sites, ranging in order of responsiveness from greatest to least, were amygdala, mammillary hypothalamus, tuberal hypothalamus, and preoptic area. The corticosterone increments obtained under anesthesia were similar in magnitude to those obtained in the absence of anesthesia. Placement of the electrodes in the median eminence itself did not enhance the responsiveness. Hind leg shock evoked a steroid increment comparable to that produced by tuberal stimulation ; and ketamine, a centrally acting drug, provided an estimate of the maximal centrally elicited response. The evidence is consistent with the view that excitatory afferent paths to corticotropin releasing factor (CRF) neurons and the CRF neurons themselves lie distributed in the tissue stimulated.