HYPERTROPHY OF OXYTOCINERGIC MAGNOCELLULAR NEURONS IN THE HYPOTHALAMIC SUPRAOPTIC NUCLEUS FROM GESTATION TO LACTATION

In the present experiments, we examined the changes in cell size (prof ile area) of oxytocinergic magnocellular neurons during reproductive s tates and dehydration with quantitative immunohistochemistry. During l actation, hypertrophy was observed in oxytocinergic magnocellular neur ons but not in vasopressinergic ones in the supraoptic nucleus. In vir gin rats, chronic dehydration increased the cell size in both oxytocin ergic and vasopressinergic neurons. After normal weaning time, the cel l size decreased, returning to virgin level within 20 days. However, i i the mothers were deprived of their litters immediately after parturi tion, the cell size rapidly returned to virgin level within 5 days. Fu rthermore, the increase in the cell size of the mothers was not affect ed by the size of their nursing litters.