Action of Dopamine To Induce Release of FSH-Releasing Factor (FRF) from Hypothalamic Tissue<i>in Vitro</i>¹

Abstract

After a 30-min preincubation period, anterior pituitaries alone or anterior pituitaries + stalk median eminence fragments were incubated for 6 hr in medium 199. Media were assayed for FSH concentration by the method of Steelman and Pohley. Incubation of anterior pituitaries in the presence of stalk median eminence tissue resulted in a slight increase in FSH release. If the combined stalk median eminence + anterior pituitary tissue was incubated with 1–5 μg/ml of serotonin, epinephrine or norepinephrine, basal release of FSH was unaltered. When dopamine was added to the incubation medium in doses of 2.5–5 μg/ml, FSH release was significantly increased (p < .01), and a dose-response relationship was observed. Dopamine in similar doses failed to alter FSH release from anterior pituitaries incubated alone. Dopamine, epinephrine, norepinephrine or serotonin at doses of 5 μg/ml did not alter the FSHreleasing action of partially purified ovine FRF. The response to dopamine was completely inhibited by 20 μg/ml of the a-adrenergic blocker, phentolamine, whereas pronethalol, a β-adrenergic blocker, not only failed to suppress the response to dopamine but in fact induced a further slight increase in FSH release. The effect of dopamine was observed only when anterior pituitary halves and stalk median eminence fragments were incubated in a ratio 2 fragments/ gland, and not when the ratio was 1 fragment/gland. (Endocrinology 86: 278, 1970)