The chick as a model for malignant hyperpyrexia.

Administration of succinylcholine (SCh) to chicks produces rigid paralysis and death due to respiratory impairment. The mechanism of the SCh effect is probably related to the multiple innervation of muscle fibres, leading to excessive intracellular accumulation of calcium. This situation may be similar to that in malignant hyperpyrexia (MH) occurring in mammals. Dantrolene sodium, phenytoin and procain, drugs used against MH, were found to afford protection against SCh rigidity and death in chicks. It is suggested that the chick can be used as a convenient model for rapid screening of drugs potentially active against NH.