THE EFFECT OF ALCOHOL INJECTION ON SUCKLING-INDUCED PRL AND ALPHA-MSHRELEASE IN LACTATING RATS

The effects of acute treatment with alcohol on prolactin (PRL) surge a nd immunohistochemical features of PRL cells and alpha-melanocyte-stim ulating hormone (alpha-MSH) cells in lactating rats were investigated. In light microscopic observations, one could see numerous large, ligh tly immunoreactive PRL cells in the pars distalis of control lactating rats. These cells revealed well-developed Golgi zones, prominently di lated ER, and a few granules in the electron microscopic observations. The alcohol-treatment depressed the occurrence of such ''active'' cel ls. In addition, following resuckling, the immunoreactivity to alpha-M SH of the intermediate lobe was decreased in light microscopic observa tions and a release of alpha-MSH granules in cells of the intermediate lobe was detected in electron microscopic observations. These changes were prevented by the injection of alcohol. These results indicate th at suckling induces an increase of the release of PRL granules from PR L-cells in the pars distalis and alpha-MSH granules from the cells in the intermediate lobe which are correlated with the appearance of the PRL surge. Further, acute administration of alcohol to lactating rats prevents both changes and consequently inhibits the suckling-induced P RL surge.