[The control of somatosensory area II of cerebral cortex on nucleus raphe magnus and its relation with nucleus accumbens].

Our previous work have demonstrated that the stimulation of somatosensory area II (Sm II) of cerebral cortex or N. accumbens (NAc) could activate nucleus raphe magnus (NRM), producing analgesia. The aim of this work is to study whether the effect of activation of Sm II on neurons in NRM is related to NAc. The spontaneous discharges of NRM neurons and their nociceptive responses induced by stimulation of tail tip were recorded extracellularly with glass microelectrode. The effects of stimulation of Sm II on the NRM neurons were observed before and after lesion of NAc. Before lesion of NAc, the stimulation of Sm II could activate NRM neurons, obviously increasing the firing rates in 0-10 minutes after stimulation (P < 0.05-0.01), and their nociceptive responses were decreased in 0-10 and 20 minutes (P < 0.01-0.001). After lesion of NAc, the firing rates having no clear change, and their nociceptive responses were even slightly enhanced. It is suggested that the effect of activation of Sm II on NRM neurons may need the relay via the NAc.