Selective effect of ethanol on the vestibular nucleus neurons in the cat

Effects of intravenous administration of ethanol on the neuronal activities of the lateral vestibular nucleus (LVN) and spinal trigeminal nucleus (STN) were investigated in cats. The LVN neurons were classified into three groups according to the latency of the first spike elicited by orthodromic vestibular nerve stimulation and antidromic vestibulospinal tract stimulation: monosynaptic, polysynaptic I and polysynaptic II neurons. Ethanol of 0.2--1.6 g/kg dose-dependently suppressed the orthodromic spike generation of the monosynaptic and polysynaptic II neurons without affecting their latency and antidromic spike generation of the former neuron. The mean spike numbers of the monosynaptic and polysynaptic II neurons were significantly decreased with ethanol over 0.4 g/kg. The polysynaptic I neuron, however, remained unaffected by the drug up to 0.8 g/kg. Similarly, the spike generation of the STN relay neuron and interneuron elicited by trigeminal nerve stimulation remained unaltered with ethanol given in doses up to 0.8 g/kg. These results indicate that small doses of ethanol more selectively interfere with synaptic transmission in the LVN monosynaptic and polysynaptic II neurons than transmission in the STN relay neurons and interneurons.