Chloride-dependent enhancement by barbiturates of gamma-aminobutyric acid receptor binding

Barbiturates enhance GABA receptor (sodium-independent) binding at 0°C to bovine brain membranes about 2-fold in chloride-containing buffer but not in chloride-free phosphate or Tris/ citrate buffer.This effect is observed in frozen and thawed, thoroughly washed membranes from various regions of bovine brain as well as washed membranes prepared from unfrozen rat cerebral cortex; it is destroyed by brief treatment of the membranes with the detergent Triton X-100.The enhancement is concentration-dependent, with approximately 250 pM pentobarbital giving 50% of the maximal effect seen with saturating 2 mM barbiturate.This effect is reversed by the GABA from Hoffmann-LaRoche, Inc.