Jpn. J. Pharmacol. 81 (3), 286 - 291 (1999)

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

Toshihiko Tanaka¹, Nozomu Murata¹ and Yoichi Yamauchi<sup>2


1</sup>Gifu Research Laboratory, JBC Inc., 52 Fukue, Kaizu-cho, Kaizu-gun, Gifu 503 - 0628, Japan
²Tokyo Research Laboratories, Pharmaceutical Division, Kowa Company, Ltd.,
2 - 17 - 43 Noguchi-cho, Higashimurayama, Tokyo 189 - 0022, Japan

Abstract: 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.

Keywords: Nipradilol, β-Blocker, Cat soleus muscle, β₂-Adrenoceptor, Isoproterenol