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-mu-M 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.