The γ-aminobutyric acid (GABA) inhibiting properties of the β-substituted γ-butyrolactone convulsant, β-isopropyl-γ-butyrolactone (βIPGBL), were studied using gigaseal recording techniques in cultured chick spinal cord neurons. βIPGBL produced a dose-dependent inhibition of GABA currents with half maximal effect at 92 μM. The effects of βIPGBL were immediate and completely reversible within minutes after exposure. The inhibition by βIPGBL showed mixed competitive and non-competitive features with little voltage-dependence. βIPGBL did not alter the GABA reversal potential nor the degree of GABA desensitization. At a single-channel level, βIPGBL markedly diminished the opening of GABA channels and decreased the mean channel open time by 30-40% without affecting the amplitude of the single-channel current.
- Spinal cord neuron
- t-Butylbicyclophosphorothionate (TBPS)
- γ-Aminobutyric acid