Effects of pimozide on the ultrastructure of the pars intermedia in the rat.
The effects of pimozide, a dopamine receptor-blocking agent, were studied in the pars intermedia of the rat. The animals received 100 microgram/100 g pimozide daily for 2, 5, 10, 15 and 20 days. Pimozide induces ultrastructural changes after 5 days of treatment. About 50% of the MSH-cells display characteristics of stimulation. Their cytoplasm is partially or totally depleted of secretory granules. The rough endoplasmic reticulum displays a network of interconnecting cisternae and ribbon-like structures. The well-developed Golgi complexes exhibit numerous dilatations of their cisternae, which contain electron-dense material. The nerve endings are not altered. Twenty days after treatment, the above-described changes have not decreased in magnitude. The present findings suggest that pimozide stimulates the mechanism of synthesis and release in some MSH-cells, most probably the elements underlying an inhibitory dopaminergic control.
D000818:Animals; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D005260:Female; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D008854:Microscopy, Electron; D010868:Pimozide / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000648:ultrastructure*; D051381:Rats
D010868:Pimozide; D009074:Melanocyte-Stimulating Hormones