Effects of alpha-methyl-p-tyrosine on monoamines and catecholamine receptors in rat cerebral cortex and neostriatum.
The effects of inhibiting the synthesis of catecholamines using alpha-methyl-p-tyrosine (alpha-MPT) were investigated in four cortical regions (cingulate, somatosensory, visual and entorhinal-piriform) as well as in the neostriatum (caudate-putamen). After acute (48 hours) treatments with alpha-MPT the endogenous NA levels were significantly reduced in all regions examined. The DA contents were also decreased in regions known to possess a dense dopaminergic innervation (neostriatum, cingulate and entorhinal-piriform cortices) but not in the somatosensory and visual areas, where DA is normally present in small amounts. Serotonin and 5-HIAA levels were either unaffected or increased. After such catecholamine synthesis inhibitions, there were no changes in the binding parameters (Bmax and Kd) of [3H]prazosin (alpha 1-receptors), [3H]idazoxan (alpha 2-receptors), [3H]dihydroalprenolol (total beta receptors) in the cerebral cortex nor in [3H]SCH23390 sites (dopamine D1 receptors) in both cerebral cortex and neostriatum. The results indicate that acute catecholamine depletions but with conservation of the fibers do not produce receptor modifications.
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Département de physiologie, Faculté de Médecine, Université de Montréal, Québec, Canada.
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D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D015306:Biogenic Monoamines / Q000378:metabolism*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology*; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects / Q000378:metabolism*; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D019805:alpha-Methyltyrosine
D001552:Benzazepines; D015306:Biogenic Monoamines; D008781:Methyltyrosines; D011941:Receptors, Adrenergic; D011954:Receptors, Dopamine; D012701:Serotonin; D019805:alpha-Methyltyrosine; D011224:Prazosin