ACTIVATION OF GABA(RHO-1) RECEPTORS BY GLYCINE AND BETA-ALANINE

NEURONS Of the vertebrate retina possess receptors for many neurotrans mitters. Particularly interesting is a new type of GABA receptor (GABA (rho)) that, in contrast to GABA(A) and GABA(B) receptors, shows very little desensitization, is not blocked by bicuculline, and is not acti vated by baclofen. Homomeric human GABA(rho 1) receptors were expresse d in Xenopus oocytes. In addition to GABA, acid related agonists, GABA (rho 1) receptors respond to glycine (Gly) and beta-alanine (beta-Ala) by generating Cl- currents that do not desensitize and are resistant to bicuculline. The half-maximal concentrations for Gly and beta-Ala c urrents were 14.2 +/- 1.3 mM and 0.66 +/- 0.11 mM respectively. The cu rrent responses to Gly and beta-Ala were blocked by picrotoxin and TBP S. The cross-sensitivity of GABA(rho 1) receptors to Gly and beta-Ala may play a role in retinal physiology.