Abstract
The effect of a new /3-stimulant, trimetoquinol, 011 skeletal muscle contraction inrabbits was studied in comparison with epinephrine and isoproterenol under pentobar-bital anaesthesia.I) Three 7-stimulants (5 to l0pg/kg i.v.) increased the twitch tension of EDLmuscles and decreased that of SQL muscles when the nerve was stimulated at l Hz. Theseresponses were independent of vascular changes. The effects of trimetoquinol and iso-proterenol were suppressed by prior injection of propranolol, and those of epinephrinewere depressed by propranolol and phentolamine.2) Under infusion of gallamine in F.DL muscle, epinephrine produced anticurare(mediated through the a-receptor) and curare-potentiating (through the p-receptor) ac-tions, and trimetoquinol and isoproterenol caused an increase in twitch tension similarto that in non-treated muscle and curare-potentiating action.In the gallaminized SQL muscle, the three drugs induced a decrease in twitch height, but, in the presence of propranolol, a reversal of the effect was observed with epinephrine andinafewcaseswithiSOPrOteren01, a!1.dtherevcrsalwasantagonizedbyphentolamine.3)Inthechronica11ydenervatedmusdes, thethrcedrugscausedadecreaseinLwitchheightandinmusde tone. These effectsbyepinephrinewereantagonizedbyproprano101andphentolamine, andthosebytheothertwodrugswerediminishedbyproprano101.4)Themechanicalresponscsofskeletalmuscletotrimetoquinolwcrethoughttobecausedthroughtheβ-adrenoceptorfromthercsultsobtainedinthepresentex-periments.β ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? trimctoquinol ?? ?? ?? ??, pentobarbital ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? cpinephrinc, isoprotercnol ?? ?? ?? ?? ?? ?? ?? ?? .1) ?? ?? ;3.. ?? ?? ?? (510μg/kgi.V.)IHz ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ( ?? ?? ) ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ( ?? ?? ) ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? .
