Effect of the 5HT1A receptor partial agonist buspirone on colorectal distension-induced pseudoaffective and behavioral responses in the female Wistar rat.

In the present study, we have evaluated the visceral analgesic property of buspirone, a 5HT(1A) receptor partial agonist, on colorectal distension-induced mean arterial pressure and behavioral changes in anesthetized and awake Wistar rats, respectively. The selection of the rat strain was based on the observation that anesthetized Wistar rats exhibited a more prominent mean arterial pressure change in response to colorectal distention when compared to other strains (Sprague-Dawley, Wistar-Kyoto and Spontaneously Hypertensive). Buspirone dose-dependently (0.1-1 mg/kg, i.v.) antagonized mean arterial pressure change over a range of distensions (10-90 mmHg). In parallel studies conducted in awake animals, buspirone (1-5 mg/kg, s.c.) attenuated the abdominal withdrawal response, a nociceptive behavior, in response to colorectal distension. This effect was antagonized by co-administration of the 5-HT(1A) receptor antagonist N-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl]-N-2- pyridinylcyclohexanecarboxamide (WAY-100635) (5 mg/kg, s.c.). We conclude that buspirone exhibits significant visceral analgesic property in two models of abdominal nociception.