Inhibitory Patterns by CB 154 of Prolactin and Growth Hormone Responses to Partially Purified Bovine Hypothalamic Extracts

Abstract

Summary

The effect of CB 154 on PRL and GH release stimulated by BHE with PRF and GRF activities was investigated in perifused rat pituitaries in vitro. The perifusion with 1.0 μg/ml of CB 154 for 260 min completely suppressed PRL release stimulated by BHE at a dose of 0.2 hypo-thalamic equivalents/1.5 ml starting at 190 min for 20 min. When the dose of BHE was raised to 0.5 hypothalamic equivalents/1.5 ml, the inhibitory effect was partially reduced. In the next study, BHE was administered twice for 20-min duration at a 70-min interval. CB 154 was administered together with the initial BHE. CB 154 inhibited PRL release not only with the initial BHE but also with the second BHE. When CB 154 was administered prior to BHE at different times for a 20-min interval, it was noticed that the longer the elapsed time between CB 154 and BHE, the stronger was the suppressive effect of CB 154 on PRL release. The basal secretion of PRL was not modified by a pulse of CB 154. Also, CB 154 did not affect BHE-mediated GH release. These results suggest that CB 154 manifests, at least in part, its inhibitory effect on PRL release at the level of the pituitary by canceling PRF activity.

We are indebted to NIAMDD Rat Pituitary Hormone Program for supplying rat GH and PRL ra-dioimmunoassay kits. The supply of 2-Br-a-ergo-cryptine (CB 154) was generously furnished by San-doz Pharmaceuticals. We thank Miss Yoshiko Ter-aoka for her technical assistance.