Increases in adrenolumbar venous flow and epinephrine secretion elicited by preoptic and hypothalamic stimulation in...

Seventy-five sites were electrically stimulated within the preoptic and hypothalamic areas of anesthetized cats (n = 16). Adrenolumbar venous blood flow, secretion of epinephrine and norepinephrine, heart rate and mean arterial blood pressure were measured at baseline and following a standard stimulus (0.6 mA for 30 s) at each site. The most frequent adrenal medullary response to central stimulation was an increase in the secretion of both catecholamines (ng/min) greater than 10% of the baseline mean. Seventeen sites (23%) increased adrenolumbar venous flow greater than 12% above the mean baseline flow rate. This group of sites also evoked significantly greater increases in the secretion of epinephrine, and in mean arterial blood pressure and heart rate. These data support the hypothesis that secreted catecholamines, especially epinephrine, may act locally to increase blood flow through the adrenal medulla.