[Facilitation of the onset of tetanic responses induced by 4-methylesculetol in amphibian isolated neuromuscular preparations].

Previous observations have shown that the 4-Methylesculetin (4ME) and the calcium provoke an increased response when the motor somatic and autonomic nerve-endings are stimolated. In the present research, we have studied the influence of the bioflavonoid and of an increased medium [Ca++] on the tetanic responses obtained from the isolated frog "sciatic nerve-gastrocnemius muscle" preparation. The 4ME has always facilitated the beginning of a complete tetanic response and has also frequently increased the developed mechanical tension. These effects appeared more evident when the bioflavonoid was employed together with the ascorbic acid. Moreover, an increased medium [Ca++] has induced similar effects. The nifedipine and the flunarizine, well-known Ca++ -antagonists, have constantly reduced or even abolished the facilitating effect induced by the bioflavonoid. On the basis of these results, we could hypothize that these observed facilitating effects are dependent on both an increased Ach-release and an increased muscle mechanical efficiency. Our previous results and also some literature data suggest that these effects could be due to an increased Ca++-passage through the cell membrane of the motor nervendings and of the muscle fibres too.