Endogenous GABA receptor ligands in hypophysial portal blood.
The concentrations of endogenous gamma-aminobutyric acid (GABA) receptor ligands were measured in hypophysial portal plasma by a sensitive and specific radioreceptor assay. Portal plasma contained higher concentrations of GABA receptor ligands than peripheral controls, although this increase was not due to authentic GABA but an unknown low-affinity ligand. Evidence is presented to support the hypothesis that the dipeptide homocarnosine may represent at least a part of this unknown. Electrical stimulation of median eminence evoked a massive (7.8-fold) increase in the rate of release of GABA (but not the low-affinity component) into portal blood. These results suggest that GABA and possibly other low-affinity ligands such as homocarnosine could serve as factors involved in the central control of anterior pituitary function.
D000612:4-Aminobutyrate Transaminase / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002336:Carnosine / Q000031:analogs & derivatives / Q000097:blood; D004558:Electric Stimulation; D008297:Male; D010902:Pituitary Gland / Q000098:blood supply*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000032:analysis*; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid / Q000097:blood
D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; C005038:homocarnosine; D005680:gamma-Aminobutyric Acid; D002336:Carnosine; D000612:4-Aminobutyrate Transaminase