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.