Dopaminergic influences on prolactin synthesis and release from rat anterior pituitary cultures

Abstract

Dopaminergic influences on prolactin release from lactotrophs have been studied using the rat anterior pituitary cell culture. The prolactin inhibiting activity of hypothalamic extracts was examined in relation to dopamine. Dopamine inhibited prolactin secretion from the rat anterior pituitary cell culture in a dose dependent fashion. The median effective dose was 2 x 10 -7 M and the maximal inhibition (70-90 ~o of the control value) was shown by 10 -5 M dopamine. Further increase in dopamine concentration did not result in any further inhibition of prolactin secretion. Dopamine antagonists such as haloperidol and (§ could inhibit the effect of dopamine on prolactin release. A Schild plot from the relationship between dopamine and (+)butaclamol in prolactin release in the anterior pituitary cell culture showed that pAz value of (+)butaclamol is 8.9 with a slope of 1.00. High concentrations of haloperidol or (+) butaclamol (both above 10-SM) caused a marked inhibition in prolactin release initially, followed by some irreversible cytotoxicity on the anterior pituitary cells. The major damage