CONCOMITANT VARIATION IN IMMUNOREACTIVITY FOR ENKEPHALINS AND NEUTRALENDOPEPTIDASE IN THE MEDIAN-EMINENCE OF THE LACTATING RAT

In the brain, neutral endopeptidase (NEP) is implicated in the biologi cal inactivation of enkephalins and substance P. NEP, enkephalins and neurokinins were detected by immunocytochemistry in the median eminenc e (ME) of lactating female rats either freely nursing or separated fro m their pups for 48 h. A significant decrease in enkephalin and NEP im munoreactivity was observed in the external zone of the ME after pup r emoval. In both animal groups, neurokinin immunoreactivity was absent from this region. These results indicate that: (1) a concomitant varia tion in immunoreactivity for enkephalins and NEP occur in the ME of th e lactating rat; (2) in the ME during lactation, NEP may essentially b e implicated in the biological degradation of enkephalins.