1. Whole cell voltage-clamp studies of γ-aminobutyric acid (GABA) receptors were performed on large (>80 μm) cultured human dorsal root ganglion (DRG) neurons. 2. GABA and pentobarbital sodium when applied in micromolar concentrations evoked inward Cl- currents in DRG neurons voltage clamped at negative membrane potentials. 3. Diazepam (10 μM) and pentobarbital (10 μM) upmodulated the GABA current by ~149 and 168%, respectively. 4. The GABA currents in human DRG cells were unaffected by the classical GABA antagonists picrotoxin and bicuculline (100 μM). In contrast, the GABA responses evoked in adult rat DRG cells cultured in an identical manner were inhibited by both antagonists. The glycine receptor antagonist strychnine (100 μM) did not alter GABA currents in human DRG cells. 5. Human DRG cells did not respond to glycine (10-100 μM) or taurine (10-100 μM). The GABA(B) agonist baclofen had no effect on the holding current when patch pipettes were filled with 130 mM KCl. The GABA(B) antagonists saclofen applied either alone or with GABA was without effect. 6. The differences between the GABA receptors described here and GABA receptors in other species may reflect the presence of receptor subunits unique to human DRG cells.
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