Intestinal distension test, a method for evaluating intermittent visceral pain in the rabbit

Behavioural response to intestinal distension was studied in 12 female New Zealand albino rabbits under various conditions. On increasing intraluminal pressures, the rabbits elicited uniform behavioural responses within discrete pressure ranges, notably a sudden pelvic withdrawal at 30-50 mmHg. The pressure provoking pelvic withdrawal was chosen as the test parameter and proved to be individually reproducible, irrespective of fasting/non-fasting or the time of day and with no signs of adaptation in six days consecutive measurements. Morphine modified the pressure response in a dose-dependent manner, whereas isotonic saline or pentobarbital had no effect. In conclusion, the intestinal distension test is reproducible and mimicks intermittent visceral pain in the rabbit. This allows for paired observations in small animal populations with a minimum of discomfort to the animals, which offers a major advantage when comparing with the existing visceral pain tests.