Effects of cocaine and pimozide on plasma and brain alpha-melanocyte-stimulating hormone levels in rats.
The effects of cocaine on rat plasma and brain alpha-melanocyte-stimulating hormone (alpha-MSH) levels have been studied by means of a specific radioimmunoassay. The selected brain areas were the hypothalamus, septum-nucleus accumbens and hippocampus. Cocaine given subcutaneously decreased the alpha-MSH levels in the peripheral blood. Pimozide, a dopaminergic antagonist, had an opposite effect: it increased the alpha-MSH levels in the peripheral blood. Combined treatment with cocaine + pimozide resulted in a decrease in the pimozide-induced increase in alpha-MSH levels in the blood. Cocaine and pimozide or the combination of cocaine + pimozide were ineffective on the alpha-MSH levels in the hypothalamus and septum-accumbens brain regions. In the hippocampus, cocaine in the dose applied induced a slight but not significant decrease in the alpha-MSH level. Pimozide caused a significant decrease in the hippocampal alpha-MSH level which disappeared at 60 min. Cocaine prevented the pimozide-induced depletion of alpha-MSH. The data indicate that cocaine may act as a dopaminergic agonist in the mechanism of control of alpha-MSH secretion from the intermediate lobe of the pituitary. The alpha-MSH levels in the brain are controlled by different mechanisms. In some brain areas, the dopaminergic system has no action; in others the mechanisms might be similar to but slightly different from that in the pituitary.
Sarnyai
Z
Z
Institute of Pathophysiology, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Vecsernyés
M
M
Julesz
J
J
Szabó
G
G
Telegdy
G
G
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003042:Cocaine / Q000494:pharmacology*; D008297:Male; D010868:Pimozide / Q000494:pharmacology*; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D000521:alpha-MSH / Q000097:blood / Q000378:metabolism*
D010868:Pimozide; D000521:alpha-MSH; D003042:Cocaine