CHEMICAL REGULATION OF THE CEREBRAL BLOOD FLOW IN CATS WITH ROSTRO- OR PREPONTINE TRANSECTION OF THE BRAINSTEM

Cerebral blood flow (CBF) and its response to hypercapnia were evaluated in cats with brainstem transected either at rostropontine (pretrigeminal preparation) or prepontine (cerveau isole preparation) le- vel. Additionally, the effect of pentobarbital on CBF response to hyper- capnia and to papaverine were examined. CBF was measured with Xe intracaroti'd injection method. Cortical EEG activity was recorded. In rostropontine cats cerebral vessels responded with a dilatation to hypercapnia. In prepontine cats CBF response to CO, was absent, where- as that to papaverine maintained. In rostropontine cats administration of pentobarbital, even in very low doses, caused disappearance of CBF response to hypercapnia, leaving that to papaverine. Our results support the idea that a neu1,ogenic mechanism is involved in chemical regula- tion of CBF. The rostra1 part of the pontine reticular formation may be responsible for this neurogenic control.