Ontogenic appearance of Na+ channels characterized as high affinity binding sites for tetrodotoxin during development of the rat nervous and skeletal muscle systems.

The appearance of the voltage-dependent Na+ channel during the fetal and post-natal development of rat brain, cerebellum and skeletal muscle has been followed using a highly radiolabelled derivative of tetrodotoxin. The number of Na+ channels is low at the fetal stage and increases drastically during post-natal development. The time-course of this increase is different in brain, cerebellum and skeletal muscle. Changes in affinity of the Na+ channel for tetrodotoxin occur during brain and cerebellum development. The results are discussed in relation with the maturation of the three types of excitable tissues.