Local anaesthetic and anti-arrhythmic actions of alprenolol relative to its effect on intracellular potentials and other properties of isolated cardiac muscle.
1. Alprenolol, a beta-adrenoceptor blocking drug reported to have the same potency as propranolol in vitro and in vivo, was found to be four times more active than procaine as a local anaesthetic on frog sciatic nerve.2. At doses of 0.125 mg/kg and above alprenolol protected anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation.3. In isolated rabbit atria, resting potentials were unchanged, and the duration of the action potential was not prolonged, by concentrations of alprenolol up to 10.5 x 10(-6)M. The maximum rate of depolarization (MRD), however, was reduced by 30% at a concentration of 0.525 x 10(-6)M. This was 214 times less than the concentration which reduced the frog action potential height by 25%.4. The concentration of alprenolol required to produce more than 15% decrease in contraction or maximum driven frequency was 3.5 x 10(-6)M.5. As a test of the direct action of alprenolol on isolated cardiac muscle, MRD was also a more sensitive test than the measurement of electrical threshold or conduction velocity.
D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000605:Amino Alcohols / Q000494:pharmacology*; D000772:Anesthesia, Local; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D001145:Arrhythmias, Cardiac / Q000188:drug therapy*; D004553:Electric Conductivity; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009467:Neuromuscular Depolarizing Agents; D011343:Procaine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D012584:Sciatic Nerve / Q000187:drug effects; D013565:Sympatholytics / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D000605:Amino Alcohols; D000779:Anesthetics, Local; D009467:Neuromuscular Depolarizing Agents; D013565:Sympatholytics; D011343:Procaine; D011433:Propranolol