Freeze-fracture studies of denervated and tenotomized rat muscle.

We studied the effects of denervation and tenotomy on the freeze-fracture ultrastructure of rat extensor digitorum longus muscle. The muscle plasma membrane was analyzed for the density of orthogonal arrays and caveolae. A period was found up to 30 days of age where innervation is required for the development and maintenance of orthogonal arrays. Denervation of older animals had no effect on the density of orthogonal arrays. The caveolar density increased after denervation at all ages. Tenotomy delayed the development of normal arrays, but had no significant effect on caveolar density. The results obtained for neonatally denervated rat muscles are similar to those seen in the muscles of patients with Duchenne muscular dystrophy.