Physiological and behavioural responses to duodenal pain in freely moving rats.

Luminal distention of the intestine can be aversive in humans and laboratory animals, and hypersensitivity to distention is found in functional gastrointestinal disorders. Current animal models either require anaesthesia or acute balloon intubation or use implanted balloons of irritant materials, for which the aversive quality of distention and physiological responses have not been well characterised. We report here that silicone balloon catheters implanted in the duodenum via the stomach have long patency without obvious tissue damage. Balloon inflation in freely moving rats caused passive avoidance learning and classic 'pain' postures, as well as graded cardiovascular responses which can be recorded telemetrically. The method should make long-lasting studies of pharmacological and environmental effects on visceral sensitivity more feasible.