Aging impairs afferent nerve function in rat intestine. Reduction of mesenteric hyperemia induced by intraduodenal capsaicin and acid.

The high incidence of peptic ulcer disease despite decreased acid secretion in the elderly suggests an impairment of mucosal defense mechanism with aging. Stimulation of the intestinal mucosal afferent nerves by intraduodenal application of capsaicin or hydrochloric acid (HCl) increases superior mesenteric artery (SMA) blood flow and protects the duodenal mucosa against deep damage. We tested the hypothesis that the intestinal hyperemia induced by intraduodenal capsaicin or HCL is significantly reduced in older (12 months) rats compared with younger (2 months) rats. Mesenteric blood flow was measured by pulsed Doppler flowmetry in anesthetized rats with the flow probe around the SMA. Two milliliters per kilogram of 160 microM capsaicin or 0.1 N HCl administered intraduodenally increased SMA blood flow significantly in both age groups. The peak response in SMA blood flow, however, was significantly smaller in the older rats than in the younger rats. These observations support the hypothesis that impairment of afferent nerve function occurs with aging in the rat intestine.