Effect of Electrical Stimulation of the Canine Diencephalon on the Secretion of ACTH, Growth Hormone (GH) and Prolactin (P)

Plasma levels of ACTH, growth hormone (GH), prolactin (Prl) and corticoids were simultaneously monitored before, during and after diencephalic stimulation in 18 pentobarbital-anesthetized dogs. Constant-current, monopolar biphasic stimulation of several regions of the canine ventral medial hypothalamus caused rapid increases in ACTH and corticoid concentrations. No increases in plasma GH were seen during stimulation, but plasma GH increased after the stimulus was turned off when the stimulating electrodes were in the arcuate-median eminence region. Plasma Prl concentration was not increased or decreased by stimulation of the ventral medial hypothalamus, but in 2 instances in 1 dog, it was increased by stimulation of the nucleus supraopticus difusus. The data indicate that different areas in the hypothalamus regulate the secretion of these 3 anterior pituitary (AP) hormones.