Influences of norepinephrine, and adrenergic agonists and antagonists on gonadotropin secretion from dispersed pituitary cells of goldfish, Carassius auratus.

Static incubations of dispersed goldfish pituitary cells with 1-100 nM norepinephrine (NE) stimulated gonadotropin (GTH) release. Additions of the alpha-agonist phenylephrine, and the alpha 1-agonist 6-fluoronorepinephrine, but not the alpha 2-agonist clonidine, nor the beta-agonist isoproterenol, also enhanced GTH secretion. The GTH responses to 1 nM NE was significantly inhibited by coincubations with 1 microM of the alpha-antagonist phentolamine, the alpha 1-antagonists prazosine and benoxathian, but not the alpha 2-antagonist yohimbine nor the beta-antagonist propranolol. The GTH responses to NE and phenylephrine were also additive to salmon GTH-releasing hormone (sGnRH)-induced GTH release. These results suggests that NE directly stimulates GTH secretion independent of sGnRH receptors via alpha 1-like adrenergic receptors.