Analysis of GABA-induced inhibition of spontaneous Wring in chick accessory lobe neurons

It has been hypothesized that chick accessory lobes (ALs) contain functional neurons and act as a sensory organ of equilibrium. It was reported that neurons located in an outer layer of ALs showed gamma-aminobutyric acid (GABA)-and glutamic acid decarboxylase (GAD)-like immunoreactivity more strongly than centrally located neurons, which were surrounded by the GAD-immunoreactive terminals. We investigated effects of GABA on the electrical activity of AL neurons. About 50% of embryonic AL neurons exhibited spontaneous Wring. In the on-cell recording, GABA, muscimol, and GABA in combination with CGP35348 inhibited this Wring. In whole-cell voltage clamp recordings, GABA and muscimol evoked a transient current. The mean reversal potential of GABA-evoked currents was close to the theoretical reversal potential of Cl-. These results indicate that GABA exerts the inhibitory effect on the Wring through the activation of GABA(A) receptors. In addition, the intracellular concentration of Cl- was estimated to be about 16 mM in measurements with the gramicidin-perforated configuration, indicating the physiological reversal potential of the GABA current was about -60 mV. In conclusion, AL neurons have an intrinsic mechanism to evoke the spontaneous Wring, which can be arrested by the inhibitory mechanism through the activation of the GABA(A) receptors.