Spinal cord stimulation attenuates visceromotor reflexes in a rat model of post-inflammatory colonic hypersensitivity

Spinal cord stimulation (SCS) has been found to relieve neuropathic and ischemic pain clinically and to attenuate a nociceptive reflex in an animal model of acute colonic hypersensitivity. The goal of the present study was to determine the effect of SCS in a rat model of post-inflammatory colonic hypersensitivity. Acute inflammation was induced in rats by a single enema of trinitrobenzenesulfonic acid (TNBS) (50 mg/kg, 0.5 ml, 25% EtOH). Control rats received a single saline enema. A visceromotor behavioral response (VMR), induced by innocuous colorectal distention (30 mm Hg, 10 min) was used to quantify the level of colonic sensitivity on day 3 and 30 post-enema. Prior to VMR testing, under general anesthesia, an electrode (cathode) was placed epidurally on the dorsal surface of the spinal cord at L1 with a paravertebral anode plate. Three to 7 days after implantation of the SCS electrode, the effect of SCS (50 Hz, 0.2 ms, amplitude 90% of motor threshold for 30 min) on colonic sensitivity was determined. On day 30, rats that had received a single TNBS enema were hypersensitive to innocuous colonic distention when compared to rats that received a saline enema (VMR/10 min: TNBS: 17.2+/-0.8 vs. Saline: 9.6+/-1.1, p<0.01). Spinal cord stimulation significantly reduced the VMR in the TNBS-enema group to a value that resembled the saline-enema group (VMR/10 min: TNBS: 11.2+/-1.2 vs. Saline: 10.0+/-1.0). This study provides the first evidence that SCS might be a potential therapeutic for the treatment of abdominal pain observed in patients with post-inflammatory irritable bowel syndrome.