Effect of verapamil and diltiazem on the rCBF and the rCBF autoregulation in cortex and thalamus of cats.

The effects of Verapamil and Diltiazem, administered at a dose of 0.3 mg/kg i.v., on the autoregulation of the regional cerebral blood flow (rCBF) in the cortex and the thalamus were studied on 28 cats. The animals were anesthetized with ether and alfa-chloralose. The rCBF was registered by the hydrogen clearance method with locally generated hydrogen. The mean arterial blood pressure (MABP) elevation was performed by an i.v. infusion of angiotensin (0.2 microgram/min). The mean initial values of the cortical rCBF were 71.15 ml/100g/min and of the thalamic rCBF -46.85 ml/100 g/min. The mean limits of the cortical rCBF autoregulation were: 137.5 mm Hg for the absolute limit (La) and 31.25 mm Hg for the relative limit (Lr). The mean limits of the thalamic rCBF autoregulation were: 157.75 mm Hg for the (La) and 46.5 mm Hg for the (Lr). Verapamil increased the cortical rCBF by 40% and the thalamic rCBF by 24%. The absolute limits of rCBF autoregulation were decreased by 22% in the cortex, and by 15% in the thalamus. The relative limits were decreased by 31% in the cortex and by 35% in the thalamus. Diltiazem increased the cortical rCBF by 42% and the thalamic rCBF by 6%. The absolute limits of rCBF autoregulation were decreased by 21% in the cortex and the thalamus. The relative limits were decreased by 52% in the cortex, and by 38% in the thalamus.