The inhibitory effects of nucleus raphe magnus stimulation on genioglossus muscle in rabbits

Experiments were done on 20 urethane anesthetized adult rabbits. It was found that: (1) Electrical stimulation to the nucleus raphe magnus (NRM) produced inhibitory effects on inspiratory activities of the genioglossus muscle. The latency of this inhibition averaged 9.0 �� 1.5 ms (mean �� SE). (2) Unit discharges in the NRM showed antidromic action potentials to stimulations to the hypoglossal nucleus. These results suggested that the NRM might exert inhibitory effects on genioglossus via monosynaptic axonal projections to the hypoglossal nucleus.