Effect of des-Tyr1-gamma-endorphin and des-Tyr1-alpha-endorphin on alpha-MPT-induced catecholamine disappearance in rat brain nuclei: a dose--response study.
The effect of des-Tyr1-gamma-endorphin (beta-LPH62-77, DT gamma E) and des-Tyr1-alpha-endorphin (beta-LPH62-76, DT alpha E), administered intracerebroventricularly (icv) in doses of 0.01, 0.1, 1 and 10 micrograms, was studied on the alpha-methyl-p-tyrosine-(alpha-MPT) induced disappearance of catecholamines in a number of microdissected rat brain regions, which were selected on the basis of the neuroanatomy of the dopamine systems in the brain and of previous observations. A dose-dependent increase in the disappearance of dopamine in alpha-MPT-pretreated rats was observed following icv administration of DT gamma E in the nucleus interstitialis striae terminalis, the paraventricular nucleus, the anterior hypothalamic nucleus and the zona incerta. In these same brain regions a decrease in the alpha-MPT-induced disappearance of dopamine was found following the administration of DT alpha E, but only after doses of 0.01, 0.1 and 1 microgram. In none of these regions were effects observed after 10 micrograms of DT alpha E. No effects were seen on dopamine utilization in the nucleus accumbens, caudate nucleus and median eminence after any of the doses of DT gamma E or DT alpha E. The alpha-MPT-induced disappearance of noradrenaline was significantly enhanced in the anterior hypothalamic nucleus of rats treated with DT gamma E. It is concluded that DT gamma E and DT alpha E induce opposite changes in the utilization of dopamine selectively in brain regions which are predominantly innervated by neurons belonging to the intradiencephalic dopamine systems.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D009928:Organ Specificity; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors*; D019805:alpha-Methyltyrosine
D004723:Endorphins; D008781:Methyltyrosines; D010446:Peptide Fragments; D019805:alpha-Methyltyrosine; C018903:gamma-endorphin, des-Tyr(1)-; C024770:alpha-endorphin, des-Tyr(1)-; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine; D009638:Norepinephrine