EFFECTS OF ADENOSINE AND 2-CHLOROADENOSINE ON CEREBRAL COLLATERAL VESSELS

Adenosine is a potent cerebral vasodilator. We tested the hypothesis t hat dilatation of collateral vessels in cerebrum, in response to topic al adenosine and 2-chloroadenosine (2-CAD), would increase blood flow to collateral-dependent cerebrum. In dogs anesthetized with halothane, a branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally. The collateral-dependent area at risk for inf arction was perfused from a reservoir with microsphere-free blood, and blood flow to normal cerebrum and to cerebrum dependent on collateral flow was measured with radioactive microspheres injected into the lef t ventricle through a femoral artery catheter. Perfusion through the c annulated MCA branch was stopped, and flow to normal and collateral-de pendent cerebrum was measured after adenosine (10(-2) M) or 2-CAD (10( -4) M) was added to the superfusate over the cerebrum. In normal cereb rum, topical application of adenosine increased flow to outer but not inner layers. Topical application of adenosine had little effect on fl ow to collateral-dependent tissue. In normal cerebrum, 2-CAD increased flow to outer layers, whereas flow to inner layers tended to increase . During 2-CAD, flow to outer cortical layers of collateral-dependent cerebrum increased from 140 +/- 20 ml/100 g/min (mean +/- SD) to 231 /- 68, whereas flow to the inner collateral-dependent tissue did not c hange. The findings indicate that, after occlusion of a cerebral arter y, topical 2-CAD increases blood flow to outer layers of collateral-de pendent and normal cerebrum. The findings suggest also that, after art erial occlusion, collateral circulation to cerebrum has dilator reserv e, and flow to tissues that are dependent on collaterals may be augmen ted.