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.

Variation in Mouse Basolateral Amygdala Volume is Associated With Differences in Stress Reactivity and Fear Learning

“…Lesions encompassing the CeA can inhibit HPA-axis responses to at least some forms of stress (Beaulieu et al, 1986;Van de Kar et al, 1991), whereas amygdala stimulation can increase glucocorticoid release (Redgate and Fahringer, 1973;Dunn and Whitener, 1986). As such, the relatively greater HPA-axis response in small BLA mice could be another manifestation of abnormal amygdala function.…”

Plasma Corticosterone Responses to Electrical Stimulation of the Amygdaloid Complex: Cytoarchitectural Specificity

“…Slusherand Hyde [26] reported that in the encephalé isolé cat significant in creases in corticosteroid levels of the adrenal venous efflu ent followed stimulation of the medial part of the basal nu cleus; decreased levels were produced by stimulation of the lateral and basolateral amygdaloid nuclei. Matheson et al [16] reported that electrical stimulation of the corticome dial, basal and lateral portions, but not of the anterior por tion of the amygdala of cats elevated corticosterone and cortisol levels, and Redgale and Fahringer [22] reported a prompt increase in plasma ACTH after stimulation of the medial amygdaloid nucleus in anesthetized cats. In con trast, in the monkey, stimulation of the basal and lateral portions but not the corticomedial part of the amygdala evoked increased plasma cortisol [6].…”

“…Increased adrenocortical activity has been reported to fol low bilateral removal of the amygdaloid and preamygdaIoid cortex of cats and dogs [17], electrolytic destruction of the amygdala of rats [32], and ablation of the medial amyg dala nuclei of deer mice [5]; decreased activity followed transection of the stria terminalis and bilateral amygdalectomy of monkeys [18]. A rise in plasma corticosteroid levels has been reported to follow electrical stimulation of the amygdala of conscious cats [16], cats during recovery stage of a long-lasting Dial anesthesia [24], pentobarbital anesthetized dogs [23], conscious rats [2], pentobarbital anesthetized rats [22] and conscious rhesus monkeys [19]. In conscious rabbits, electrical stimulation of the amygdala in creased the biosynthetic activity of the adrenal cortex [13].…”

Review: Reducing Handling Stress Improves Both Productivity and Welfare

“…Over 20 different animal studies show that electrical stimulation of the amygdala will trigger both behavioral and autonomic responses that resemble fear in humans (15). In cats and rats, stimulation of the amygdala will increase plasma corticosterone levels (68,78,83). Lesions in the amygdala will block both conditioned and unconditioned fear responses (15), giving further evidence of the role of the amygdala as the fear center of the brain.…”