Effects of Several β-Blockers On Blood Pressure in the Rat

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