Effect of adenosine and dipyridamole on cerebral blood flow

The purpose of these experiments was to determine whether infusions of adenosine and of dipyridamole, which raise levels of endogenous adenosine, increase cerebral blood flow (CBF). In anesthetized dogs and cats, intracarotid infusions of adenosine increased blood flow to cranial muscle but did not alter CBF (measured with microspheres). Anatomical limitations may prevent satisfactory examination of cerebral vascular responsiveness during intracarotid infusion of vasodilator drugs in these species. In anesthetized rabbits, infusion of adenosine 10 microM/min in the carotid artery produced a 2-fold increase in CBF. Infusion of dipyridamole 20 microM/min increased CBF 2.7-fold. Dipyridamole produced a small decrease in cerebral oxygen consumption, which indicates that the vasodilator effect of the drug is not an indirect effect secondary to increased metabolism. These data indicate that exogenous and endogenous adenosine increase CBF in rabbits.