THE INFLUENCE OF ADRENAL CORTICAL INSUFFICIENCY UPON THE RESPONSE OF MUSCLE TO MOTOR NERVE STIMULATION, WITH PARTICULAR REFERENCE TO THE FIFTH STAGE OF NEUROMUSCULAR TRANSMISSION

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Abstract
The response of muscle to motor nerve stimulation at a frequency of 60/sec. was studied in normal anesthetized cats and in anesthetized cats whose adrenals had been removed from 24-48 hrs. previously. At this frequency of stimulation, the height of the initial contraction and the rapidity of onset of fatigue were not significantly different in the normal and the adrenalectomized animals. Such cortical adrenal insufficiency, however, prevented or seriously impaired the development of the 5th stage (recovery after development of fatigue) of neuromuscular transmission. This defect was in large measure corrected by desoxycorticosterone acetate. Expts. involving stimulation at frequencies of 2 per sec. and 30 per sec. showed that at these frequencies fatigue occurred more rapidly in the adrenalectomized than in the normal animals, but not rapidly enough to account for the failure of the 5th stage on the basis of contraction fatigue. The possibility that the failure of the 5th stage to develop may be secondary to other effects of adrenal insufficiency such as a circulatory inadequacy is considered.

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