Sex differences in central adrenergic control of vasopressin release

Central adrenoreceptor-mediated regulation of vasopressin secretion and cardiovascular function was studied in male rats and female rats in specific estrous cycle phases. In conscious, unrestrained rats with intracerebroventricular (icv) cannulas and femoral artery and vein catheters, plasma arginine vasopressin concentration (PAVP), mean arterial blood pressure (MABP), and heart rate (HR) were determined before and 5 and 15 min after icv injection of 10 micrograms norepinephrine or 50 micrograms phenylephrine. Norepinephrine (icv) increased PAVP in proestrus and metestrus four and three times (P less than 0.01 and 0.05, respectively) more than in males. Norepinephrine induced similar MABP elevations (P less than 0.01) in males and females in all cycle phases; HR decreased only in proestrus, estrus, and metestrus (P less than 0.01). The increase in PAVP after icv phenylephrine was four and three times greater in proestrous and diestrous females (P less than 0.01 and 0.05, respectively) than in males. The proestrous MABP rise was three times that in males (P less than 0.05); HR decreased similarly in diestrus, proestrus, and males. These results suggest gonadal steroid hormones influence adrenoreceptor-mediated control of vasopressin secretion, MABP, and HR.