Morphine and electroacupuncture: comparison of the effects on the cortical evoked responses after tooth pulp stimulation in rats.

The effects of morphine and electroacupuncture on the cortical evoked responses after tooth pulp stimulation were investigated in rats. Morphine suppressed these responses more strongly in secondary somatosensory areas than those in primary somatosensory areas, while electroacupuncture suppressed the responses to the same degree in both areas. These results might suggest that there are some differences in noxious-suppressive action between morphine and the endogenous opiates released by electroacupuncture stimulation.