Functional α₃-glycine receptors in rat adrenal

The adrenal medulla contains high-affinity strychnine binding sites, presumed to be receptors for glycine. In this study, glycine injection (400 pmol) via a cannula attached to a microdialysis probe increased in vivo concentrations of catecholamines in the adrenal microdialysate in anesthetized rats. Strychnine perfusion (20 pmol/20 min) blocked these responses. To identify receptors potentially mediating this effect, we tested for RNA transcripts of the three known α subunits of strychnine binding site, using the reverse transcription-polymerase chain reaction. Only mRNA encoding the α₃ isoform was found in the rat adrenal. The findings suggest that in the rat adrenal, glycine stimulates catecholamine release by binding to strychnine binding sites and that those sites probably contain the α₃ isoform.