PHARMACOLOGICAL PROPERTIES OF GAMMA-AMINOBUTYRIC ACID(A) RECEPTORS FROM ACUTELY DISSOCIATED RAT DENTATE GRANULE CELLS

The pharmacological properties of gamma-aminobutyric acid (GABA) type A receptor (GABAR) currents recorded from hippocampal dentate granule cells acutely dissociated from 28-35-day-old rats were characterized u sing the whole-cell patch-clamp technique. Granule cells were voltage- clamped to 0 mV, and GABA was applied using a modified U-tube rapid-ap plication technique, All granule cells were moderately sensitive to GA BA (EC(50) = 47 mu M) All granule cell GABAR currents were uniformly s ensitive to Zn2+ (IC50 = 29 mu M), diazepam (EC(50) = 158 nM), zolpide m (EG(50) = 75 nM), and dimethoxyl-4-ethyl-beta-carboline-3-carboxylat e (IC50 = 60 nM). GABAR currents from only 50% of granule cells were s ensitive to loreclezole (EC(50) = 9 mu M). These data suggest that hip pocampal dentate granule cells expressed GABARs with distinctive pharm acological properties of two types: loreclezole-sensitive and -insensi tive receptors. It is likely that these distinctive properties were du e to the specific GABAR subtypes that assembled to produce distinct gr anule cell GABAR isoforms.