MIF-I and postsynaptic receptor sites for dopamine.
In an attempt to determine the mechanism by which the tripeptide l-prolyl-l-leucyl-glycine amide (PLG, MIF-I) exerts its antiparkinsonian effect, the action of this substance on various postsynaptic components of striatal dopaminergic nerves was studied. It was shown that injection of rats with MIF-I (1 mg/kg, IPX5, 24 hr intervals) did not alter tyrosine hydroxylase, dopa decarboxylase, choline acetyltransferase and glutamic acid decarboxylase activities in the striatum under the conditions tested. The activities of adenylate cyclase, dopamine-stimulated adenylate cyclase, and guanylate cyclase were not altered in vitro by various concentrations of MIF-I (0.1 to 1000 micrometer), although VIP and neurotensin had some effect. Also the rate of uptake of 3H-dopamine by rat striatal synaptosomes was unchanged, as was the binding of 3H-dopamine and 3H-spiperone to beef caudate membranes. This series of studies indicates that MIF-I does not act directly on the striatal dopamine postsynaptic receptor under the conditions tested, although it is possible that MIF-I could act indirectly at this or another site in vivo by releasing or activating some other factor.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000201:enzymology; D004298:Dopamine / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects* / Q000378:metabolism; D013134:Spiperone / Q000378:metabolism; D013569:Synapses / Q000187:drug effects
D011954:Receptors, Dopamine; D013134:Spiperone; D009075:MSH Release-Inhibiting Hormone; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D004298:Dopamine