Effects of ethanol applied by electrosmosis on neurons in the lateral and medial vestibular nuclei.

Electrophysiological studies were performed to elucidate the effects of ethanol on neuron activities in the lateral vestibular nucleus (LVN) and medial vestibular nucleus (MVN) of cats using an electrosmotic and microiontophoretic method. The LVN and MVN neurons were classified into two types according to the firing pattern and latency of the first spike with vestibular nerve stimulation: monosynaptic and polysynaptic neurons. Electrosmotic application of ethanol up to 200 nA produced a dose-dependent inhibition of spikes of the LVN monosynaptic neurons with vestibular nerve stimulation and iontophoretically applied glutamate, but no significant alterations of the spikes of the LVN polysynaptic neurons. Acetylcholine-induced firing in the LVN monosynaptic neurons was also inhibited by ethanol. In the MVN, spike generation of the monosynaptic and polysynaptic neurons with vestibular nerve stimulation and iontophoretically applied glutamate remained unaltered with ethanol up to 200 nA. These results indicate that ethanol predominantly inhibits synaptic transmission of the LVN monosynaptic neurons, probably by acting on the postsynaptic cell bodies.