Sensitization of postsynaptic dorsal column neuronal responses by colon inflammation

THE role of a newly identified component of the postsynaptic dorsal column (PSDC) system in viscerosensory processing has been recently described. The purpose of this study was to examine the effect of colon inflammation on the responses of single PSDC cells, located in the vicinity of the central canal at L6-S1 spinal segments, to graded colorectal distension (CRD) and to cutaneous stimulation. Experiments were conducted on seven male Sprague-Dawley rats anesthetized with pentobarbital. Recordings were made from seven PSDC cells located around the central canal at L6-S1 in response to CRD and cutaneous stimulation before and after colon inflammation. Inflammation of the colon with mustard oil (MO) induced an increase in the background activity of these cells. Colon inflammation also potentiated the responses of the PSDC cells to graded CRD but not to cutaneous stimulation. This is consistent with previously observed effects of colon inflammation on the responses of viscerosensitive cells in the ventral posterolateral (VPL) nucleus of the thalamus and in the nucleus gracilis (NG). These observations support a role of the PSDC system in viscerosensory processing and primary visceral hyperalgesia.