Interactions between visceral nociception and tactile inputs / 中国病理生理杂志

ABSTRACT

AIM: To study the interactions between skin tactile and visceral nociceptive inputs in the ventroposterior lateral (VPL) nucleus of the rat thalamus. METHODS: Visceral nociceptive inputs were generated by colorectal distension (CRD). Skin tactile inputs were generated by 10 Hz skin puff. They were delivered in sequence to investigate the changes in reaction to the test stimulus after the conditioning stimulation. RESULTS: Among the isolated 78 single VPL neurons that had response to both CRD and skin tactile stimuli, 44% (31/70) had their response to CRD reduced by the preceding conditioning tactile stimulation, and 54% (38/70) had their tactile response enhanced by the preceding CRD. The skin receptive fields of the majority of the cells were located along the caudal part of the Meridians of Stomach and Gallbladder of Chinese medicine. CONCLUSIONS: (1) Conditioning tactile inputs may inhibit noxious colorectal inputs, but this effect was short-lasting and limited at single neuron level. (2) On the other hand, pre-existing visceral nociception may cause abnormally high discharge of thalamic neurons, a phenomenon that may be related to the clinically seen allodynia on the body surface in visceral lesions.