Neurochemical studies of the mesolimbic dopaminergic pathway: glycinergic mechanisms and glycinergic-dopaminergic interactions in the rat ventral tegmentum.
The rat ventral tegmentum (containing somata and dendrites of mesolimbic dopaminergic neurones) contained 1.3 mumol/g wet weight of glycine. Slices of ventral tegmentum accumulated exogenous [3H]glycine by an energy-, temperature- and sodium-dependent mechanism. The uptake was medicated by two different transport systems; one system with relatively low affinity for glycine (Km approximately 400 microM) and the other a higher affinity for glycine (Km approximately 10 microM). Small amino acid analogues of glycine inhibited the uptake process, the most potent being taurine and beta-alanine (47% and 44% inhibition, respectively, at 1 mM). Release of exogenous [3H]glycine by elevated potassium and by protoveratrine A was calcium-dependent and tetrodotoxin-sensitive. Glycine (500 microM--2mM) potentiated the protoveratrine A-induced release of exogenous [3H]dopamine from slices of ventral tegmentum; this potentiation was blocked by atrychnine (10 microM). A convulsant dose of strychnine elevated the concentration of 3,4-dihydroxyphenylacetic acid in the ventral tegmentum. Glycine is likely to be a transmitter in the ventral tegmentum and to have a role regulating the activity of somatodendritic regions of mesolimbic dopaminergic neurones.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013331:Strychnine / Q000494:pharmacology; D013681:Tegmentum Mesencephali / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature
D000596:Amino Acids; D015102:3,4-Dihydroxyphenylacetic Acid; D013331:Strychnine; D005998:Glycine; D004298:Dopamine