Somatovisceral interactions in the rat dorsal column nuclei

Recent studies have revealed that noxious visceral inputs travel in the dorsal column pathway, and interactions between colorectal noxious and tactile inputs occur in the ventrobasal thalamus. This investigation was to test whether the somatovisceral interactions also take place in the dorsal column nuclei (DCN). Forty-five single DCN neurons of anesthetized rats responsive to colorectal distension (CRD) all had excitatory responses to tactile stimuli, and their tactile responses were predominantly (32/45 units) enhanced by preceding CRD. Their responses to CRD were reduced in half (22/44) units when preceded by tactile stimulation. Despite these generally similar response features in comparison with the thalamic recordings, there were however different response properties in DCN neurons, suggesting that somatovisceral interactions take place at multiple levels in the dorsal column-medial lemniscus system.