Postsynaptic dorsal column pathway of the rat. II. Evidence against an important role in nociception.

The response characteristics of neurons at the origin of the postsynaptic dorsal column (PSDC) pathway were determined in unanesthetized, decerebrated, spinalized rats. Sixty-four percent of PSDC neurons responded only to innocuous mechanical stimuli. Thirty-six percent responded to innocuous stimuli but were more powerfully activated by noxious pinch. Ninety-three percent of the tested PSDC neurons were not activated by any of several intensities of sustained, repeated noxious heating of their receptive fields. The failure of pinch-responsive PSDC cells to respond to thermal stimulation, even in sensitized skin, suggests that they do not receive a functionally significant input from C polymodal nociceptors, heat nociceptors, or mechanical-heat nociceptors. We conclude, therefore, that the postsynaptic dorsal column pathway is not importantly involved in nociception in the rat.