[EXPRESS] Ethanol-induced enhancement of inhibitory synaptic transmission in the rat spinal substantia gelatinosa.

Recent studies have shown that ethanol produces a widespread modulation of neuronal activity in the CNS. It is not fully understood, however, how ethanol changes nociceptive transmission. We investigated acute effects of ethanol on synaptic transmission in the substantia gelatinosa (SG, lamina II of the spinal dorsal horn) and mechanical responses in the spinal dorsal horn. In SG neurons, bath-application of ethanol at low concentration (10 mM) did not change the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs). At medium to high concentrations (20-100 mM), however, ethanol elicited a barrage of large amplitude sIPSCs. In the presence of TTX, such enhancement of IPSCs were not detected. In addition, ethanol (20-100 mM) increased the frequency of spontaneous discharge of vesicular GABA transporter (VGAT)-Venus labelled neurons, and suppressed the mechanical nociceptive response in wide-dynamic range neurons in the spinal dorsal horn. The present results suggest that ethanol may reduce nociceptive information transfer in the spinal dorsal horn by enhancement of inhibitory GABAergic and glycinergic synaptic transmission.