Brainstem influences on transmission of somatosensory information in the spinocervicothalamic pathway

The inhibition of somatosensory responses of lateral cervical nucleus neurons resulting from stimulation of the brainstem has been investigated. Single unit extracellular recordings were obtained from neurons in the lateral cervical nucleus of chloralose-anesthetized cats. Electrical stimulation of the periaqueductal gray, nucleus raphe magnus, nucleus cuneiformis, and nuclei reticularis gigantocellularis and magnocellularis was found to be very effective in inhibiting the responses of lateral cervical nucleus neurons evoked by electrical or tactile stimulation of the skin. Additional experiments were performed to determine whether the inhibitory effects were mediated in the spinal cord dorsal horn or in the lateral cervical nucleus. These experiments which examined the effect of brainstem stimulation on the responses induced by stimulation of the dorsolateral funiculus or on the antidromic latency of activation of lateral cervical nucleus neurons from thalamus, revealed that most and possibly all the inhibition could be accounted for by an action on the spinal cord. These results are consistent with other studies showing that spinocervical tract cells in the spinal cord can be inhibited by stimulation of the same brainstem regions.