The Neuromuscular Blocking Action of Suxamethonium on the Rat Diaphragm

Abstract

Experiments are described using the rat isolated phrenic nerve diaphragm preparation, in which suxamethonium produced a neuromuscular block consisting of an initial phase of fairly sharp onset followed by a prolonged phase, which first remained at a steady level and then slowly decreased in intensity over several hours. Suxamethonium block is antagonised by potassium and intensified by tubocurarine in both phases. It would therefore appear that the depolarising action of suxamethonium is complicated by some measure of competitive inhibition in the isolated nervemuscle preparation as in the intact animal.THE nature of the neuromuscular block produced by suxamethonium showed a marked species variation. Zaimis (1953) reported some competitive features of the block in monkeys, dogs, rabbits and hares. However, on isolated rat and kitten phrenic nerve diaphragm preparations, Stovner (1958) showed that the neuromuscular block produced by succinylmonocholine was more competitive in nature than that produced by suxamethonium.There is much clinical evidence for the existence of a mixed neuromuscular block produced by suxamethonium. Grant (1952), Ruddell (1952), Hodges (1953, Guerrier andWilliams (1954), andBrennan (1956) have reported reversal of prolonged suxamethonium paralysis by neostigmine in man and in other intact animals. EXPERIMENTAL MethodThe details of the dissection and assembly of the apparatus were those described by Bulbring (1946) and modified by Chou (1947). The fanshaped muscle strip was stimulated indirectly through the phrenic nerve at 6/min. with supramaximal rectangular pulses of 0.1 to 0.3 m-sec. duration. Muscle contractions were recorded by a spring-loaded lever. The muscle was immersed in a bath containing Tyrode solution modified by halving the concentration of calcium chloride (bringing the concentration nearer to the ionised concentration in the blood) (McDowall, Miechowski and Shafei, 1949), and reducing the concentration of magnesium chloride from 0.01 to 0.0025 per cent (Taugner and Fleckenstein, 1950). The fluid was aerated with 95 per cent oxygen and 5 per cent carbon dioxide. The capacity of the bath was 75 ml. and the temperature was maintained constant in all experiments _ af 0.25". Doses referred to are in terms of suxamethonium btomidc;,~ potassium chloride and tubocurarine chloride. 177

Meningkatkan Kreativitas Anak Usia 5-6 Tahun melalui Kegiatan Menganyam Menggunakan Bahan Alam

“…Bahan alam merupakan bahan atau material yang ada di alam sekitar. Bahan alam terdapat di alam dan ditemukan di tahan atau bagaian dari hewan atau tumbuhan (Whittaker, 2004). Bahan alam juga terdapat diluar atau dapat diperoleh dekat tempat tinggal kita (Miller, 2009).…”