Papers of the Week

The purpose of this study was to determine effects and mechanisms of sacral nerve stimulation (SNS) on visceral hypersensitivity in rodent models of colonic hypersensitivity. SNS was performed with different sets of parameters for 30 minutes in six regular rats. Visceral sensitivity was assessed by the measurement of electromyogram (EMG) and abdominal withdrawal reflex (AWR) before and after SNS. Real/sham SNS with optimized parameters was performed in eight restraint stress-induced visceral hypersensitivity rats and 10 neonatal acetic acid treated colonic hypersensitivity rats, acute effect of SNS was assessed by comparing EMG and heart rate variability (HRV). Neonatal acetic acid treated rats were treated by SNS (n=10) or sham-SNS (n=10) daily for 7 days for the assessment of the chronic effect of SNS. (1)When the stimulation amplitude was reduced from 90% of motor threshold (MT) to 65% or 40% MT, SNS with certain parameters showed an inhibitory effect on AWR. The best stimulation parameters for SNS was "14Hz, 330μs, and 40% MT". (2)SNS significantly reduced visceral hypersensitivity and improved autonomic function in restraint stress-induced rats. The inhibitory effect was blocked by naloxone.(3)Acute and Chronic SNS significantly reduced visceral hypersensitivity and improved autonomic function in acetic acid treated rats. SNS with reduced stimulation strength may be used to treat colonic hypersensitivity and the best stimulation parameters seem to be"14Hz, 330μs and 40% MT". SNS with optimized parameters improved visceral hypersensitivity in rodent models of colonic hypersensitivity mediated via the autonomic and opioid mechanisms.