Abstract
We have studied membrane channels activated by gamma-aminobutyric acid (GABA) in adrenal medullary chromaffin cells by using patch-clamp techniques. These channels share many properties with GABA-receptor channels in the central nervous system. They are chloride-selective, blocked by the GABA antagonist bicuculline, and reversibly desensitized at high GABA concentrations. The dose-response curve has a slope of 2 in the Hill plot, indicating a bimolecular binding reaction of GABA to the receptor. Single-channel currents display multiple conductance states as do glycine-activated chloride channels in mouse spinal neurons. Gating properties of GABA-activated channels, as described by a sequential model for agonist-activated channels, are similar to gating properties in central neurons. GABA-induced currents are potentiated by diazepam, indicating that anxiolytic drugs like the benzodiazepines might be involved in the regulation of anxiety states in the peripheral nervous system.