[Studies on changes of the plasma prolactin, growth hormone and ACTH levels following surgical stress and epidural micro-injections of morphine hydrochloride as a postoperative analgesic method].

Epidural micro-injection of morphine hydrochloride is very useful for the postoperative analgesic method. In this study, we investigated the relationship between appearance of amelioration of pain and the plasma prolactin (PRL), growth hormone (GH) and ACTH levels following epidural morphine. The plasma PRL levels significantly elevated with surgical stress. Following epidural morphine, the plasma PRL levels significantly decreased in the effective cases, and significantly increased in the ineffective cases. Following epidural morphine, the plasma ACTH levels significantly decreased in the effective cases, and insignificantly increased in the ineffective cases. The duration to onset of amelioration of pain was prolonged with intravenous injections of metoclopramide (MCP) before epidural morphine. We concluded that patterns of PRL and ACTH releases following epidural morphine were correspondent with the analgesic effect, and that appearance of amelioration of pain following epidural morphine may depend upon the dopaminergic mechanism.