Effects of nimodipine and flunarizine on the regional autoregulation of the CBF in cats.

The effects of nimodipine (3 micrograms/kg/min) and flunarizine (60 micrograms/kg/min) on the autoregulation of the regional cerebral blood flow (rCBF) in the cortex and thalamus of 28 cats were studied. The animals were anaesthetized with ether and alfa-chloralose. The rCBF was registered by the hydrogen clearance method with locally generated hydrogen. MABP elevation was performed by i.v. angiotensin infusion (0.2 +/- g/min). The initial values of the rCBF in the cortex were 71.1 ml/100g/min, and in the thalamus - 49.1 ml/100g/min. The limits of rCBF autoregulation in the cortex were: the absolute limit of autoregulation (La) 139 +/- 11 mm Hg, and the relative limit of autoregulation (Lr), 28 +/- 6 mm Hg. In the thalamus these values were: La 160 +/- 11 mm Hg, and Lr 47 +/- 7 mm Hg. Nimodipine increased the rCBF in the cortex by 58 per cent, and in the thalamus, by 38 per cent as compared to the initial values (p < 0.01). The limits of rCBF autoregulation in the cortex changed to 88 +/- 8 mm Hg for the La, and to 10 +/- 4 mm Hg for the Lr (p < 0.01); and in the thalamus, to 92 +/- 8 mm Hg for the La, and to 19 +/- 5 mm Hg for the Lr (p < 0.01). Flunarizine increased the rCBF in the cortex by 28 per cent, and in the thalamus by 24 per cent, as compared to the initial values (p < 0.01). The rCBF autoregulation in both cerebral structures was not influenced by flunarizine.