Somatic pain sensitivity during formation and healing of acetic acid-induced gastric ulcers in conscious rats

A classical feature of visceral pain is its referring to somatic locations. Gastric ulcer is a source of visceral pain. In the present study we investigated whether gastric ulcers may trigger the changes in somatic nociception. For this aim somatic pain sensitivity was estimated under conditions of gastric ulcer development and healing. Gastric ulcers were induced by luminal application of 60% acetic acid under surgical conditions. Control rats were subjected to the same surgical procedure, but with the application of saline instead of the acid. Somatic pain sensitivity (tail flick latency), plasma corticosterone level, adrenal and thymus weight were investigated under conditions of the formation and the healing of gastric ulcers. The application of the acid resulted in the formation of kissing gastric ulcers, the increase of somatic pain sensitivity (the decrease of tail flick latency) as well as the appearance of typical signs of chronic stress: long-lasting increase of plasma corticosterone level, adrenal gland hypertrophy and thymus gland involution. Natural healing of gastric ulcers was accompanied by restoration of pain sensitivity as well as attenuation of the signs of chronic stress. Delay of ulcer healing by the daily indomethacin administration (2 mg/kg, s.c.) prevented the restoration of somatic pain sensitivity. The results suggest that chronic gastric ulcers may trigger somatic hypersensitivity.