Indirect cholinergic vasomotor control of intestinal blood flow in the domestic chicken.

1. A histochemical and pharmacological study has been made of the relationship between the medial circular and adventitial longitudinal smooth muscle coats of the anterior mesenteric artery of the domestic chicken.2. The longitudinal (LM) coat was found to be innervated by excitatory cholinergic and inhibitory adrenergic nerves, confirming previous reports.3. The circular (CM) coat was found to be innervated by adrenergic vasoconstrictor nerves. There was no evidence for the existence of cholinergic nerves supplying the circular muscle.4. Contraction of the LM had little effect on the resting perfusion pressure of the isolated artery, but caused potentiation of perfusion pressure responses to vasoconstrictor stimuli directly affecting the CM.5. It is suggested that the function of the LM is to modulate the reactivity of the anterior mesenteric artery to vasomotor stimuli, and that this may be particularly implicated in the cardiovascular response to sudden stress.