Cholinergic mediation in the ventral tegmental area of alpha-melanotropin induced excessive grooming: changes of the dopamine activity in the nucleus accumbens and caudate putamen.
The effect of alpha-melanotropin (alpha-MSH) on the rat mesolimbic dopaminergic activity was estimated by measuring the changes in dihydroxyphenyl acetic acid (DOPAC) and dopamine (DA) endogenous levels in the nucleus accumbens (Ac) and caudate putamen (CP). A marked increase of DOPAC/DA ratios resulting from an increase in DOPAC and decrease in DA levels was found in the Ac 30 and 65 min after bilateral alpha-MSH-injections (1 microgram) into the ventral tegmental area (VTA). Similar changes were observed in the CP 65 min post-injections. These peptide-induced changes were completely inhibited by a previous VTA injection of atropine (1 microgram), at a dose that totally blocked the alpha-MSH-induced excessive grooming and motor activation. These results confirms that alpha-MSH affects a cholinergic afferent to the VTA which modifies the mesolimbic dopaminergic system involved in the alpha-MSH/ACTH-induced behaviors.
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Instituto de Investigación Médica Mercedes y Martín Ferreyra, Córdoba, Argentina.
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D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002421:Caudate Nucleus / Q000378:metabolism; D002794:Choline / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D006120:Grooming / Q000187:drug effects* / Q000502:physiology; D007700:Kinetics; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000378:metabolism; D011699:Putamen / Q000378:metabolism; D051381:Rats; D013681:Tegmentum Mesencephali / Q000187:drug effects / Q000502:physiology*; D000521:alpha-MSH / Q000494:pharmacology*
D015102:3,4-Dihydroxyphenylacetic Acid; D000521:alpha-MSH; D008464:Mecamylamine; D001285:Atropine; D002794:Choline; D004298:Dopamine