| Abstract: | Changes in the distribution of Ach-sensitivity in two types of muscle fibers in the tail of the tadpoles as well as the innervation pattern of these fibers have been investigated during metamorphosis. It was shown by iontophoretic application of acetylcholine that the entire muscle membrane exhibits Ach-sensitivity only during premetamorphosis. Ultrastructural studies revealed mature nerve-muscle junctions at this stage of development of the tadpoles. At later stages (prometamorphosis), Ach-sensitivity decreased and finally (climax) became restricted by the innervation region. It is suggested that special neurotrophic regulation of extra-junctional Ach-sensitivity takes place in myotomal muscles of the tadpoles. |
