Abstract
Effects of practolol, alprenolol and pindolol on blood pressure in the rat were studied. Also effects of these three β-blocking agents on blood pressure and heart rate in spinal rats during adrenaline infusion were studied and compared with those of propranolol. The β-blocking agents produced a sustained pressor action in the rat, and in the spinal rat infused with adrenaline. The magnitude of the pressor action induced by the β-blockers was in the following order: pindolol≥propranolol≥alprenolol>practolol. Minimum doses of these β-blockers required to cause a pressor action in the spinal rat infused with adrenaline were in the following order; practolol>alprenolol≥propranolol≥pindolol. The magnitude of the pressor action produced by the same dose of these β-blockers and minimum doses of these β-blockers required to cause a pressor action in the spinal rat infused with adrenaline seemed to be roughly proportional to their β-receptor blocking activities. It was concluded that the minimum doses of these β-blockers required to cause a pressor action and the magnitude of the pressor action induced by the β-blockers in the spinal rat infused with adrenaline could be used to compare their β-blocking activities and that practolol, a cardioselective β-blocker, seems to block not only cardiac β-receptor but to some extent also peripheral vascular β-receptors.
