Assessment of visceral sensitivity using radio telemetry in a rat model of maternal separation

Stress plays an important role in the development of visceral hypersensitivity, a key mechanism underlying the pathophysiology of the irritable bowel syndrome. Visceral sensitivity in rats is generally assessed under restrain conditions. To avoid this potential stress factor, we developed a model using implanted radio telemetry for remote measurement of the visceromotor response (VMR) to colorectal distention (CRD). Ten days after implantation of a radio telemetry transmitter and EMG electrodes, visceral sensitivity was evaluated by applying a standardized distension protocol (1, 1.5 and 2 mL) on three different days. In a second series, visceral sensitivity was assessed in maternally separated rats before, directly after and at 6 and 24 h after water avoidance (WA) stress. CRD resulted in a reproducible VMR response on the three different study days. in separated but not in non-handled rats, WA significantly increased visceral sensitivity at 6 h (P = 0.006) and 24 h (P = 0.004) after WA. Our results show that radio telemetry is a reliable and well tolerated new tool for evaluating visceral sensitivity in rats. These data further confirm that maternal separation is a good model for evaluating the mechanisms underlying visceral hypersensitivity.