Cardiovascular chemoreflexes from the perfused innervated ileum of the cat

The vascular supply of innervated segments of ileum in urethan-anesthetized cats was perfused by an electrolyte-glucose solution, containing heparinized cat blood. Addition of acetylcholine or nicotine to the perfusion inflow was followed by increases of systemic arterial pressure. Calculated mean concentrations of 32 mug/ml acetylcholine or 35 mug/ml nicotine in the perfusion fluid induced mean pressor responses of 19 and 23 mmHg. These responses began within 2-6 s, reached a maximum within 20 s, were unaffected by vagotomy, and were frequently accompanied by cardiac acceleration and increase in rate and depth of respiration. Evans blue in the perfusion fluid did not enter the general circulation. Systemic responses were abolished or markedly decreased after perfusion of 40-180 mg procaine through the innervated gut segments or by cooling the nerve fibers between the perfused ileum and the body of the animal. In itself, procaine injected into the isolated circulation or nerve cooling commonly induced decreases of arterial pressure. The vascular isolation of the perfused segments and the dependence of the systemic responses on the nervous connections indicate that the effects were reflex.