Effect of acetylcholine on cerebral circulation.

Effects of intravertebral, intracarotid, and intravenous infusion of acetylcholine on cerebral blood flow (CBF) and metabolism was studied in 17 baboons anesthetized with pentobarbital. We measured CBF by the bilateral jugular venous outflow technique using two electromagnetic flowmeters. Effect of acetylcholine infusion on cerebral vascular response to hypercapnia was also assessed. Intravertebral infusion of acetylcholine (0.01 mg/kg/min) increased CBF by 27% and cerebral metabolic rate for oxygen by 19% and decreased cerebral vascular resistance by 25%. On intracarotid injection of acetylcholine, only an 8% increase in CBF was observed, and intravenous infusion produced no change in the parameters observed. Acetylcholine administered by any of the three routes did not enhance the CBF response to hypercapnia. Increase in CBF on intravertebral administration of acetylcholine is associated with an arousal effect and an increase in cerebral metabolism.