Effects of ethanol on vestibular nucleus neurons responding to sinusoidal rotation

Effects of ethanol applied by electro-osmosis were examined on the rat vestibular nucleus neurons responding to vestibular nerve stimulation and horizontal sinusoidal rotation. Ethanol (50-150 nA) inhibited the neurons monosynaptically activated by vestibular nerve stimulation and also suppressed the activity of the type I neuron, which responded with an increase in firing on ipsilateral rotation and a decrease on contralateral rotation. However, the drug did not affect the type II neuron, which showed the opposite response to the ipsi- and contralateral rotation compared with the type I neuron. Iontophoretic application of atropine (25-50 nA) inhibited spontaneous and rotation-induced firing in both type I and II neurons. These results suggest that ethanol inhibits the type I neuron projecting to the abducens nucleus, thereby impairing the vestibulo-ocular reflex.