Peptidergic nerves mediate post-nerve stimulation hyperemia in rat gut

Peptidergic nerves mediate post-nerve stimulation hyperemia in rat gut. Am. J. Physiol. 263 (Gastrointest. Liver Physiol. 26): G29-G37, 1992.-Cessation of perivascular nerve stimulation (NS) elicits a transient increase in intestinal blood flow above the prestimulatory value. This enhancement of blood flow con-stitutes the phenomenon of post-nerve stimulation hyperemia (PSH). We investigated the involvement of peptidergic sensory nerves in intestinal PSH. In anesthetized rats the velocity of blood flowing through the anterior mesenteric artery (VBF) was measured with a pulsed Doppler velocimeter. PSH was induced by 4 min of postganglionic electrical NS (5 Hz). PSH was abol-ished by distal periarterial application of tetrodotoxin and in-tra-arterial lidocaine, which suggests a peripheral sensory ner-vous mechanism for PSH. The increase in conductance at peak PSH was blocked by pretreatment with the selective, primary afferent neurotoxin capsaicin administered as 1) subcutaneous injection in neonatal life, 2) topical application to periarterial nerves, or 3) injection into the jejunal lumen. In rats pretreated with reserpine, NS evoked a hyperemic response, which was blocked by capsaicin. Treatment with adenosine deaminase in-hibited PSH considerably less than capsaicin, suggesting a lesser role for adenosine in PSH. Our findings support the hy-pothesis that postganglionic NS activates both adrenergic and peptidergic nerves and that the latter release vasodilator pep-tides in the gut during PSH. neuropeptides; autoregulation; capsaicin; mesenteric circula-tion; afferent nerves; sympathetic nerves; adenosine POST-NERVE STIMULATION HYPEREMIA (PSH) occurs in certain circulatory beds after cessation of perivascular nerve stimulation (NS). The observed increase in blood flow above the control value constitutes the PSH phe-nomenon (17). The hyperemia of a related phenomenon, autoregulatory escape, has been observed in different regional circulations in response to vasoconstricto