Diazepam-insensitive GABA(A) receptors on postnatal spiral ganglion neurones in culture

Using dissociated spiral ganglion cell cultures obtained from 3-day-old rat cochlea, we investigated the response of auditory neurones to γ-aminobutyric acid (GABA) using patch-clamp techniques. In our recording conditions, GABA elicited inward currents in > 95% of the neurones which reversed around 0 mV. Similar inward currents were measured using isoguvacin, a specific agonist of GABA(A) receptors. GABA-gated currents were reversibly inhibited by the channel blocker picrotoxin and the GABA competitive antagonist bicuculline. These functional GABA(A) receptors are characterized by an insensitivity to benzodiazepines and a relatively high sensitivity to β-carbolines and barbiturates. These results show that the GABA(A) receptor pharmacological properties of spiral ganglion neurones are close to those of cerebellar granule cells.