Different effects of harmine on plasma concentrations of L-dopa and on cerebral dopamine metabolism in rabbits and rats.
The effects of short-term intravenous administration of harmine, a monoamine oxidase inhibitor, on the plasma concentrations of L-Dopa and on dopamine levels in the brain striata of rats and rabbits after L-Dopa administration were studied. Harmine affects the L-Dopa plasma concentrations in rabbits but not in rats: in fact in the former species the area under the concentration-time curve observed after administration of L-Dopa alone increased significantly when animals were pretreated with harmine. Dopamine striatal levels increased in concert with plasma L-Dopa concentrations after administration of L-Dopa in rats and rabbits. However pretreatment with harmine resulted in a significant increase of dopamine levels in the brain striata of rabbits only. These results suggest that harmine or one of its metabolites affect the brain dopamine system not merely as a type A monoamine oxidase inhibitor but with a modulatory effect, without a precise indication of site or mode of action of harmine.
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Laboratorio di Farmacologia, Istituto Superiore di Sanità, Roma, Italia.
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D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D003342:Corpus Striatum / Q000737:chemistry; D004298:Dopamine / Q000032:analysis*; D006247:Harmine / Q000494:pharmacology*; D006719:Homovanillic Acid / Q000032:analysis; D007275:Injections, Intravenous; D007980:Levodopa / Q000097:blood* / Q000494:pharmacology; D008297:Male; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar
D007980:Levodopa; D006247:Harmine; D004298:Dopamine; D006719:Homovanillic Acid