End-plate desensitization: Specificity of calcium

The activation-desensitization sequence of muscle end-plate receptors induced by carbamylcholine has been studied in isotonic Ca2+ and isotonic Mg2+ Ringer solutions. Desensitization occurred more rapidly in the calcium solution although the extent of receptor activation was similar in both solutions. The results demonstrate that even in high concentration, Mg2+ does not exert an action on desensitization comparable to that of Ca2+.