The Acute Cerebrovascular Effects of Intracarotid Adenosine in Nonhuman Primates

In this study we sought to determine the acute cerebrovascular effects of intracarotid adenosine by using realtime cerebral blood flow (CBF) measurements in nonhuman primates. The internal carotid arteries of healthy anesthetized baboons were transfemorally cannulated. Changes in CBF were continuously measured at baseline and with 6 increasing doses of adenosine (0.002 to 1.5 mg/min) by use of an intraparenchymal thermal diffusion (TD) probe. Each infusion lasted 5 min. At baseline and at the largest dose of adenosine, CBF was also determined by the intraarterial Xe-133 technique. TD measurements revealed a dose-dependent increase in CBF from 32 +/- 6 mL . 100 g(-1) . min(-1) at baseline to 90 +/- 38 mL . 100 g(-1) . min(-1) with the largest dose of adenosine (n = 5; P < 0.0001). A similar magnitude of increase in CBF was also observed with Xe-113 CBF measurements. No significant increases in intracranial pressure or adverse systemic hemodynamic side effects were observed during adenosine infusion. The increase in CBF after adenosine lasted only for the duration of drug infusion. In conclusion, the transient cerebrovascular effects of intracarotid adenosine make it suitable for a trial of intraarterial vasodilator therapy and for controlled manipulation of cerebrovascular resistance.