alpha-MSH and Pro-Leu-Gly-NH2 (PLG; MIF-1): influence on dopamine (DA) uptake in crude synaptosomal preparations from rat mediobasal hypothalamus (MBH) and caudate putamen (CP).
The uptake of tritiated dopamine [3H] (DMI insensitive DA uptake) by synaptosomal fractions isolated from rat mediobasal hypothalamus (MBH) and caudate putamen (CP) was measured in the presence of different concentrations of alpha-melanocyte stimulating hormone (alpha-MSH) and Pro-Leu-Gly-NH2 (PLG; MIF-1) which is an inhibitor of alpha-MSH release. Compared to control, [3H]DA uptake increased significantly when the synaptosomal fraction of CP was incubated with 0.1 and 1 microM of alpha-MSH and also when the rat was previously injected with alpha-MSH. A simultaneous reduction of endogenous dopamine content was observed. Kinetic studies suggest that the enhanced uptake induced by alpha-MSH 1 microM is the consequence of the rise in Vmax, without changes in the apparent km. The uptake of [3H]DA in hypothalamic (MBH) preparations on the other hand, was not modified by the presence of alpha-MSH. PLG did not have any significant effect on [3H]DA uptake either in the CP or in the MBH. alpha-MSH may act as a modulator of the dopaminergic nigrostriatal system and the results obtained incubating CP synaptosomes in its presence demonstrate a possible direct modulator action by alpha-MSH on the terminal area of the substantia nigra neurons.
D000818:Animals; D001590:Benztropine / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D003891:Desipramine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000378:metabolism*; D007700:Kinetics; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D011699:Putamen / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D001590:Benztropine; D009074:Melanocyte-Stimulating Hormones; D009075:MSH Release-Inhibiting Hormone; D003891:Desipramine; D004298:Dopamine