Vulnerability of gastric and small intestinal mucosa to ulcerogenic action of indomethacin in C57/BL6/J mice and transient receptor potential channel vanilloid type 1 knockout mice.

Capsaicin-sensitive sensory nerves are densely distributed in the gastrointestinal system and involved in maintenance of gastrointestinal mucosal integrity. capsaicin selectively stimulates nociceptive neurons and its action is mediated through the transient receptor potential channel vanilloid type 1 (TRPV1) receptor. Activation TRPV1 receptors that play a fundamental role in pain signaling, may also exert protective effects against gastrointestinal injury. The present study was performed to investigate and compare the vulnerability of gastric as well as small intestinal mucosa to ulcerogenic action of indomethacin (IM) in mice with genetically deleted TRPV1 receptor (TRPV1 KO) and in C57/BL6/J mice. IM-induced injury was assessed macroscopically as well as histologically; the somatic pain sensitivity was estimated by tail flick latency (tail flick test); plasma corticosterone levels and body weight were also monitored. A single IM administration (35 mg/kg, subcutaneously) into pre-starving (24 h) mice caused the formation of gastric erosions 4 h later and, then, after refeeding, induced formation of the small intestinal injury which was visible 24, 48, 72 h after IM administration. Although IM-induced gastrointestinal injury was detectable in both C57/BL6/J and TRPV1 KO mice, area of gastric damage was greater in C57/BL6/J than in TRPV1 KO mice, whereas the small intestinal injury (48 and 72 h after IM injection), on the contrary, prevailed in TRPV1 KO mice compared to C57/BL6/J mice. In 24 h after IM injection, the total area of intestinal injury did not differ in C57BL6/J and TRPV1 KO mice, however histological score was higher in TRPV1 KO mice than C57BL6/J mice. TRPV1 KO mice showed the increased tail flick latencies and the lacking IM-induced corticosterone rise. The data suggest that in TRPV1 KO mice the gastric mucosa is less vulnerable to ulcerogenic action of IM compared to C57/BL6/J mice, however, their small intestinal mucosa, on the contrary, is more vulnerable to the ulcerogenic action than in C57/BL6/J mice.