[Relationship between neurons in the nucleus raphe magnus and motor reflex evoked by noxious stimulation]

The article reviews the main results of recent years study on the relationship between neurons in nucleus raphe magnus (NRM) and moving reflex evoked by noxious stimulation, including: 1. Relative phasic discharge frequency change of on-cell and off-cell in NRM occurred when tail-flick reflex (TF) evoked by noxious stimulation. The relative phasic activity of on-cell and off-cell in NRM was decreased or lost when TF was inhibited by brain stimulation and morphine analgesia. The data suggested that on-cell and off-cell in NRM participated in descending inhibition on spinal cord. 2. The initial EPSPS on neurons of NRM always occurs after the initial digastric EMG elicited by tooth pulp shock. 3. There is a positive feedback loop of reciprocal excitation between descending pathway from NRM and ventral horn neurons projecting to NRM of spinal cord. It was suggested that motor neuron pool in spinal cord possible involved in the mechanism of descending inhibition from the NRM.