[Effects of ethanol and norepinephrine injected into nucleus hypoglossus on the genioglossal muscle activities].

Integrated genioglossal and phrenic muscle activities were recorded on 87 urethane anesthetized, vagotomized rabbits to study the effect of ethanol and norepinephrine (NA) injected into nucleus hypoglossus on the potentiating effects of integrated genioglossal and phrenic muscle activities (PIMA). It was found that ethanol could inhibit PIMA of genioglossal muscle. Peak amplitude of PIMA (PAMP) was reduced with the latency of PIMA (LAT) prolonged and recovery time (RT) shortened. Norepinephrine facilitated PIMA, which could be blocked by Tolazolin. Local administration of ethanol (2 mol/L 1 microliter) to the caudal part of the 4th ventricle floor produced statistically significant reduction in genioglossal muscle activities (P < 0.01) in resting respiration. The present results suggest that ethanol exerts inhibitory effect on genioglossal muscle activity which may be associated with the inhibition of nucleus hypoglossus per se or caudal part of the 4th ventricle floor. The excitatory activity of genioglossal muscle may be mediated by noradrenergic receptors in the nucleus hypoglossus.