Influences of norepinephrine and alpha-adrenergic mechanisms on gonadotropin secretion in female goldfish, Carassius auratus.

Intraperitoneal or intraventricular (3rd cranial ventricle) injection of norepinephrine (NE) caused an increase in serum gonadotropin (GtH) concentrations in female goldfish at times of the year when the ovaries were regressed or at early stages of recrudescence, but had no influence at other stages of the ovarian cycle. In a previous report it was shown that clonidine (alpha-agonist) increased serum GtH levels in fish at early or mid-ovarian recrudescence [J. P. Chang, A. F. Cook, and R. E. Peter (1983) Gen. Comp. Endocrinol. 49, 22-31]; however, intraperitoneal injection of clonidine had no effect on circulating GtH levels when tested in fish at late ovarian recrudescence. In fish at early stages of ovarian recrudescence, intraperitoneal injection of phentolamine (alpha-blocker) did not alter GtH levels, but it blocked the NE-induced increase in serum GtH levels when injected simultaneously with NE. These results suggest that NE stimulates GtH release by alpha-adrenergic mechanisms at the brain and/or pituitary level in female goldfish in a sexually regressed or early ovarian recrudescence condition.