TY - JOUR
AU - Cheung, Cecilia Y.
AB - Previous studies performed to elucidate an anterior pituitary site of action for β-endorphin (B-EP) in the regulation of prolactin (PRL) release have been inconclusive. The purpose of the present study was to further investigate if B-EP could stimulate PRL release by a direct action at the anterior pituitary. Anterior pituitaries from ovariectomized rats were dispersed, and the cells were plated in Ham’s F-10 medium. Following a 48-hour preincubation period, the effects of B-EP on basal PRL release and on the dopamine-inhibited PRL release were studied over a 24-hour period. Overall, B-EP at concentrations ranging from 10<sup>–8</sup> to 10<sup>–6</sup> M had no effect on basal release of PRL at 1, 3, 5 and 24 h, although a small but significant increase of 39% was observed with 10<sup>–6</sup> M B-EP at 1 h of incubation only. B-EP at 10<sup>–6</sup> M, but not at lower concentrations, significantly suppressed the inhibitory effects of 10<sup>–6</sup> M dopamine on PRL release at 1 h but not at longer periods of incubation. Pretreatment of the cells for 3 h with 10<sup>–6</sup> M naloxone completely antagonized the suppressive effect of B-EP on the dopamine-mediated inhibition of PRL release. Naloxone pretreatment of the cells had no effect on basal nor dopamine-inhibited release of PRL. Because of the high concentration of B-EP required to suppress the dopamine inhibition and the transitory nature of this B-EP effect, it is unlikely that the primary site of action for B-EP in regulating PRL release is at the anterior pituitary. However, high concentrations of B-EP may antagonize the inhibitory effect of dopamine on PRL release at the anterior pituitary through a specific opiate-mediated mechanism.
TI - Does β-Endorphin Modulate Basal and Dopamine-Inhibited Prolactin Release by an Action at the Anterior Pituitary?
JO - Neuroendocrinology
DO - 10.1159/000124028
DA - 1984-01-01
UR - https://www.deepdyve.com/lp/karger/does-endorphin-modulate-basal-and-dopamine-inhibited-prolactin-release-8nCUaDbfHO
SP - 489
EP - 495
VL - 39
IS - 6
DP - DeepDyve
ER -