EFFECTS OF NALOXONE, METACLOPRAMIDE AND DOMPERIDONE ON PLASMA-LEVELS OF PROLACTIN AND LH FOLLOWING SUCKLING IN THE FEMALE RABBIT

Saline, naloxone, domperidone or metaclopramide was injected into lact ating rabbits immediately before suckling. Blood samples were taken pr ior to injection (0 minutes) and then at 15, 30, 45 and 60 minutes aft er the start of suckling, after which the samples were assayed for pla sma prolactin and LH concentrations. In all the does there was a signi ficant increase in prolactin concentration, which was highest 15 minut es after the start of suckling, and which declined exponentially there after to levels significantly higher than before suckling. The increas e in prolactin concentration was similar in does given saline and nalo xone, but it was significantly enhanced in does given metaclopramide; with domperidone the increase was intermediate and not significantly d ifferent from that following treatment with saline. In does given sali ne, domperidone, and metaclopramide plasma LH concentrations declined slowly during the hour after suckling but the concentration was increa sed significantly in does given naloxone. The inverse correlations bet ween prolactin and LH were low weak and were not significant.