EFFECTS OF ESSENTIAL OIL OF CROTON ZEHNTNERI, AND OF ANETHOLE AND ESTRAGOLE ON SKELETAL-MUSCLES

Extracts of the essential oil of Croton zehntneri (CzEO) yield a mixtu re of substances in which the major components are anethole and estrag ole. The action of CzEO and of pure anethole and estragole (at 0.05-1. 0 mg/ml) were studied in muscle preparations of the toad and rat. All three oils blocked twitches evoked by nerve stimulation. In the rat di aphragm direct stimulation resulted in enhanced twitches (CzEO), parti ally depressed twitches (estragole) and anethole did not induce a sign ificant change. The response of toad rectus to acetylcholine was reduc ed by all three oils. Caffeine contractions of the rectus abdominis an d sartorius muscles were enhanced by all oils. This enhancement in the case of the sartorius was blocked by procaine. Lowering the temperatu re to 4 degrees C in the presence of CzEO, anethole or estragole provo ked a contraction which could be blocked by procaine. CzEO, anethole o r estragole alone sometimes caused contractions. The occurrence of thi s response was increased by elevation of calcium (to 22 mM). Other div alent cations and La3+ were also effective, in order: La3+ > Ca2+ > Mn 2+ > Ba2+ > Mg2+ except in the case of anethole where the order of Ca2 + and Mn2+ are interchanged. CzEO- and estragole-induced contractions were blocked by procaine. The data suggest that CzEO, anethole and est ragole may have two sites of action on muscle fibers: the post junctio nal membrane, by blocking neuromuscular transmission, and on the sarco plasmic reticulum (SR), by increasing myoplasmic calcium.