Transforming growth factor alpha-mediated gastroprotection against stress ulceration in the rat: involvement of capsaicin-sensitive sensory neurons.

Exogenously administered TGF alpha has been shown to protect rodent gastric mucosa against injury caused by acid-dependent and acid-independent injury. The present study examined whether the gastroprotective effects of TGF alpha on stress-induced gastric ulceration in the rat involves activation of capsaicin-sensitive sensory neurons. Fasted male SD rats were subjected to water restraint stress (WRS) for four hours. Thereafter, rats were euthanized; the stomach opened and macroscopic areas of gastric ulceration quantitated (mm(2)). Gastric tissue contents of TGF alpha and the sensory neuropeptide, calcitonin gene-related peptide (CGRP) were determined by radioimmunoassay. Prior to stress rats received TGF alpha 50, 100 or 200 microg/kg by intraperitoneal injection. Sensory denervation was accomplished by high dose capsaicin treatment. WRS caused severe ulceration in the gastric corpus; 46.1 + 6.6 mm(2). Parenteral administration of TGF alpha caused dose-dependent reduction in gastric injury: 34.7 + 4.9 mm(2) with 50 microg/kg (p < 0.05); 25.4 + 3.6 mm(2) with 100 microg/kg (p < 0.001) and 9.4 + 0.8 mm(2) with 200 microg/kg (p < 0.001). The gastroprotective action of TGF alpha (200 microg/kg, i.p.) was abolished by capsaicin-induced sensory denervation. In addition, WRS ulceration was associated with significant reduction in gastric CGRP (-42%) and TGF alpha (-48%) content. Reduction in CGRP content was prevented by TGF alpha pretreatment. We conclude that: 1) TGF alpha caused dose-dependent gastroprotection against WRS ulceration, 2) TGF alpha-mediated gastric mucosal protection was prevented by capsaicin-induced sensory denervation and, 3) stress-induced injury was associated with significant reduction in gastric content of both TGF alpha and CGRP.