The external Ca(2+)-dependence of acetylcholine-induced contracture in single innervated and denervated skeletal muscle cells in mice.

We examined morphological differences and compared the Ca(2+)-dependence between acetylcholine (ACh)-contractures in normal and denervated skeletal muscle cells. ACh (1 microM - 1 mM) contracted the normal cells into a jackknife-shape. The higher the concentration of external Ca2+, the greater the ratio of responding cells/total cells observed and the sharper the angles of the "jackknives". ACh contracted the denervated cells into a compression-form, and the contraction was dependent on the external Ca2+. These results indicate that ACh-contractures in both normal and denervated cells are external Ca(2+)-dependent.