Effects of beacon on the rat pituitary-adrenocortical axis response to stress

Beacon is a peptide expressed in the rat hypothalamus and adrenal cortex, which is involved in the central regulation of feeding and inhibits basal and agonist-stimulated glucocorticoid secretion from adrenocortical cells. In vivo studies on beacon have not yet been carried out, and therefore we investigated the effects of a subcutaneous (sc) injection of beacon on the response of rat hypothalamo-pituitary-adrenal axis to stress. Handling and sc injection per se elicited a moderate increase in the plasma concentrations of ACTH and corticosterone, which was counteracted by beacon. Similarly, beacon dampened ACTH and corticosterone responses to ether stress. In contrast, beacon did not affect ACTH response to cold stress, although it was able to induce a moderate lowering in the corticosterone response. Taken together, these findings allow us to draw the following conclusions: i) beacon inhibits handling/injection- and ether stress-activated, but not cold stress-activated, neural mechanism(s) responsible for stimulation of ACTH secretion and the ensuing increase in corticosterone production; and ii) the beacon-induced dampening in corticosterone response to stress also involves a direct inhibitory effect on the adrenal-cortex secretory activity. The physiological relevance of beacon as endogenous anti-stress agent remains to be evaluated.