Effect of papaverine on regional cerebral blood flow and small vessel blood content

The effect of intravenous infusion of papaverine HCl, (2.0-2.5 mg/kg) on regional cerebral blood flow and small vessel blood content in anesthetized rats was determined. Cerebral blood flow was measured in the cerebral cortex, diencephalon plus midbrain, cerebellum, pons and medulla by means of the uptake of iodo[14C]antipyrine. Small vessel blood content was determined by labelling the plasma siderophilin with 59FeCl3. Cerebral blood flow showed interregional variation under control conditions. Papaverine increased flow in all regions, but the effect was greater in the hind compared to the forebrain. Papaverine did not significantly alter small vessel blood content or calculated open capillary density, indicating it had no functional effect upon cerebral precapillary sphincters, and therefore only affected cerebral arterioles.