Tubocurarine sensitivity of the diaphragm after limb immobilization.

The effect of immobilization of a limb on subsequent sensitivity of the diaphragm to d-tubocurarine was examined in the guinea pig. A forelimb was immobilized in a plaster cast for 1 or 3 weeks. An isolated nerve-diaphragm preparation was then set up and the sensitivity to d-tubocurarine measured. Parallel assays on a nerve-lumbrical muscle preparation from the limb in the cast were also examined for comparison. The diaphragm from unimmobilized animals showed the normal decreased sensitivity relative to the lumbrical. After immobilization the sensitivity of the lumbrical decreased, whereas that of the diaphragm did not change. Thus in contrast to previously observed behavior in limb muscles, changes in d-tubocurarine sensitivity produced by immobilization do not involve the diaphragm.