COLOCALIZATION OF PACAP, BUT NOT OF VIP, WITH OXYTOCIN IN THE HYPOTHALAMIC MAGNOCELLULAR NEURONS OF COLCHICINE TREATED AND PITUITARY-STALK SECTIONED RATS

Previous studies indicated that PACAP and VIP immunoreactive perikarya cannot be visualised in the magnocellular system of intact Sprague-Da wley rats but they are easily stained in intact sheep and cats. In rat s we had to use colchicine treatment for demonstrating PACAP immunorea ctivity. Therefore in the present investigations PACAP and VIP immunor eactivities and their colocalization with oxytocin were studied in the magnocellular system of rat hypothalamus after colchicine treatment a nd pituitary stalk section. Like colchicine treatment, section of the pituitary stalk was able to induce the appearance of both PACAP and VI P immunoreactive perikarya in the supraoptic and paraventricular nucle i and following stalk section course fibers immunopositive for both pe ptides were found in both layers of the median eminence. With the use of double labeling, PACAP immunoreactivity was partially colocalized w ith oxytocin. However, there was no colocalization between VIP and oxy tocin immunoreactivities.