[Effect of prefrontal cortex on the neuronal activity of the nucleus raphe magnus in rats]

The unit discharge of neurons in nucleus raphe magnus (NRM) were recorded with glass microelectrodes in 33 waking and tubocurarine-immobilized rats. It is observed that effects of the noxious stimulation and prefrontal cortex (PFC) stimulation on spontaneous discharges of NRM neurons and effects of PFC stimulation on noxious-evoked discharges of NRM neurons by stimulating sural nerve. The results indicated that noxious stimulation and PFC stimulation could increase spontaneous discharge of most (68.18% and 60.82% respectively) NRM neurons. It was also noted that most (49/80) NRM neurons altered their spontaneous discharge in response to noxious stimulation and PFC stimulation in a similar manner. The remainder (31/80) opposite manners. PFC stimulation could alter the response of NRM neurons to noxious stimulation. PFC stimulation could enhance or reduce noxious-evoked discharge in NRM neurons which alter their spontaneous discharge in response to noxious stimulation and PFC stimulation in a similar manner. PFC stimulation could reduce noxious-evoked discharge in NRM neurons which alter their spontaneous discharge in opposite manners. The above results suggest that PFC and NRM have a functional relation. PFC could modulate nociceptive response and it might be partly responsible for influence on activity of neurons in NRM.