β-ADRENERGIC STIMULATION OF PROLACTIN RELEASE FROM SUPERFUSED PITUITARY CELL AGGREGATES1

Abstract

1-Isoproterenol (1–ISO), a specific agonist of β-adrenergic receptors, evoked a prompt rise of prolactin (PRL) release from superfused anterior pituitary cell aggregates established in culture for 5 days. The effect was concentration-dependent between 1 and 100 nM. d-Isoproterenol was more than 2 orders of magnitude weaker than the 1-isomer. When dopamine receptors were blocked with domperidone, PRL secretion was also stimulated by 1-epinephrine (E) and 1-norepinephrine (NE), the rank order of potency being 1–ISO > E» NE. Under the l a t t e r conditions dopamine and the a-adrenergic agonists clonidine and phenylephrine, had no stimulatory effect at 1 μM. Stimulation of PRL release by 1–ISO and E was blocked by the p-receptor antagonist, propranolol, but not by the a-receptor blocker, prazosin.