The Effect of Nipradilol on the Isoproterenol-Induced Depression of Contractions in the Cat Soleus Muscle

The effect of nipradilol on the isoproterelol-induced depression of contractions of the soleus muscle of the anesthetized cats was studied. Isoproterenol (0.3 μg/kg) injected intravenously decreased the tension and degree of fusion of incomplete tetanic contractions of the soleus muscle of the anesthetized cats. The effect of isoproterenol was blocked by nipradilol (≧3 μg/kg), desnitro-nipradilol (≧10 μg/kg) and propranolol (≧10 μg/kg), but not by nitroglycerin (10-100 μg/kg). Nipradilol (30 μg/kg) and desnitro-nipradilol (300 μg/kg) almost completely antagonized the depressor effects of isoproterenol. These results coupled with evidence that nipradilol does not penetrate the blood-brain barrier indicate that nipradilol exerts an anti-tremor action by blocking peripheral β2-adrenoceptors.