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

The effects of acute treatment with alcohol on prolactin (PRL) surge and immunohistochemical features of PRL cells and alpha-melanocyte-stimulating hormone (alpha-MSH) cells in lactating rats were investigated. In light microscopic observations, one could see numerous large, lightly immunoreactive PRL cells in the pars distalis of control lactating rats. These cells revealed well-developed Golgi zones, prominently dilated ER, and a few granules in the electron microscopic observations. The alcohol-treatment depressed the occurrence of such ''active'' cells. In addition, following resuckling, the immunoreactivity to alpha-MSH of the intermediate lobe was decreased in light microscopic observations 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 that suckling induces an increase of the release of PRL granules from PRL-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 PRL surge.