PHARMACOLOGICALLY NOVEL GABA RECEPTOR IN HUMAN DORSAL-ROOT GANGLION NEURONS

1. Whole cell voltage-clamp studies of gamma-aminobutyric acid (GABA) receptors were performed on large (>80 mu m) cultured human dorsal roo t ganglion (DRG) neurons. 2. GABA and pentobarbital sodium when applie d in micromolar concentrations evoked inward Cl- currents in DRG neuro ns voltage clamped at negative membrane potentials. 3. Diazepam (10 mu M) and pentobarbital (10 mu M) upmodulated the GABA current by simila r to 149 and 168%, respectively. 4. The GABA currents in human DRG cel ls were unaffected by the classical GABA antagonists picrotoxin and bi cuclline (100 mu M) In contrast, the GABA responses evoked in adult ra t DRG cells cultured in an identical manner were inhibited by both ant agonists. The glycine receptor antagonist strychnine (100 mu M) did no t alter GABA currents in human DRG cells. 5. Human DRG cells did not r espond to glycine (10-100 mu M) or taurine (10-100 mu M) The GABA(B) a gonist baclofen had no effect on the holding current when patch pipett es were filled with 130 mM KCl. The GABA(B) antagonists saclofen appli ed either alone or with GABA was without effect. 6. The differences be tween the GABA receptors described here and GABA receptors in other sp ecies may reflect the presence of receptor subunits unique to human DR G cells.