[Study on the neuroendocrinological control of prolactin release in early puerperium]

Abstract

The purpose of this study is to investigate the neuroendocrinological control mechanism of prolactin (PRL) acting on the hypothalamo-pituitary axis during early puerperium. The puerperal women consisted of three groups: the breast-feeding group (n = 39), the bromocriptine (BRC)-treated group (5 mg/day, n = 17) and naloxone-treated group (1 mg iv, n = 16). In each group, 10 mg metoclopramide (MCP), 500 micrograms TRH or 400 mg cimetidine was given intravenously. 1) The plasma PRL levels increased significantly after the injection of MCP, TRH and cimetidine. The peak values of delta PRL levels were 447.0 +/- 62.3 ng/ml after MCP, 278.3 +/- 65.1 ng/ml after TRH and 86.5 +/- 27.3 ng/ml after cimetidine. 2) This PRL increase after the injection of MCP and cimetidine was suppressed significantly by pretreatment with BRC. However, the PRL increase after TRH was not suppressed by pretreatment with BRC. 3) Naloxone had no significant effect on PRL response to MCP and TRH, since the plasma PRL levels rose significantly after the injection of MCP and TRH in the naloxone-treated group. These results revealed that there were different mechanisms of PRL release in MCP and TRH. Furthermore, the PRL releasing mechanism was influenced by histamine H2-receptor, but was not influenced by opioid peptide in early puerperium.