[The control of somatosensory area II on the descending inhibiting pain activity of nucleus raphe magnus].

The aim of the present work is to observe the effects of somatosensory area II (Sm II) on the descending inhibiting pain activity of nucleus raphe magnus (NRM). The unit discharges in NRM and its responses to noxious stimulation of tail tip were extracellularly recorded with glass microelectrode. The bilateral Sm II was stimulated by fixed electrodes. Electroacupuncture (EA) of "Zusanli" was applied for 5 minutes. Both effects were compared at the same NRM neurons. It was found that stimulation of Sm II could activate the excitatoy-neurons in NRM (n = 10), significantly increasing their spontaneous discharges and decreasing their nociceptive responses during 0-20 minutes (P < 0.05-0.001). Similar results were observed after "Zusanli" EA, increase of their spontaneous discharges during 0-10 minutes and at 20th minute, and decrease of their nociceptive responses during 0-25 minutes were statistically significant (P < 0.05-0.001). The results were analysed with the linear regression, it was shown that the effects of Sm II stimulation and "Zusanli" EA on the spontaneous discharges and their nociceptive responses of NRM neurons were very similar in level and trend, being the positive correlation (P < 0.01-0.001). It is suggested that Sm II can activate the excitatory neurons in NRM, and it is possible that the effect of EA of "Zusanli" on NRM neurons is partially caused by activating Sm II.