The effect of some foreign anions on suxamethonium blockade of the isolated rat diaphragm preparation

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Abstract
1 . The pharmacology of suxamethonium blockade of the rat phrenic nerve-diaphragm preparation has been studied in the presence of some foreign anions. 2 . Blockade proceeded in two distinct phases in both normal and modified Krebs solution. 3 . In normal Krebs solution the characteristics bore no close resemblance to either depolarizing or competitive type blockade. 4 . In the presence of foreign anions the characteristics of the blockade more closely resembled those of depolarization. 5 . There was an increase in the sensitivity of the motor end-plate region of the muscle to the depolarizing action of acetylcholine, carbachol and suxamethonium in the presence of the anions. 6 . Although the anions enhanced the depolarizing activity of suxamethonium, the blocking potency of the drug was unaltered. 7 . It is suggested that end-plate depolarization plays little part in suxamethonium blockade of the isolated rat diaphragm and that desensitization is the primary cause of the blockade.