Hypothalamic norepinephrine mediates limbic effects on adrenocortical secretion

The purpose of this study was to elucidate the role of norepinephrine (NE) in the mediation of adrenocortical responses following limbic stimuli. The effects of stimulation of the dorsal and ventral hippocampus and the midbrain reticular formation on the plasma corticosterone (CS) levels was studied in rats with vehicle or 6-hydroxydopamine (6-OHDA) injected bilaterally into the paraventricular nucleus of the hypothalamus (PVN). The injection of 6-OHDA caused a very significant reduction in the concentration of PVN NE and blocked the rise in plasma CS following the stimulation of the above three limbic structures. The basal CS level and the response to ether stress were not affected. The present study supports previous observations on the stimulatory role of NE on CS secretion and that the modulatory effects of extrahypothalamic limbic structures on the adrenocortical activity depend on the presence of NE in the PVN.