Abstract
SUMMARY: Pretreatment of salt-maintained adrenalectomized mice for 6 days with 3–6 mg dried thyroid gland, or with 0·25 μg of either l-thyroxine or l-triiodothyronine, per mouse per day, delayed the early onset of both neuromuscular and muscular failure which are characteristic of these animals. Dose-effect curves for the action of thyroxine on the myoneural junctions and striped muscle fibres are given. A concentration of 0·05μg l-triiodothyronine/100 ml. bath fluid antagonized potassium reduction of the maximal twitch of the normal rat diaphragm in response to nerve stimulation, but not in response to direct stimulation of the curarized muscle.