Acceleration of neuromuscular re-innervation by triiodothyronine.

The right sciatic nerve was crushed in 84 rats, 42 of which were injected daily with triiodothyronine (T3; 1-0 mug/kg body weight, subcutaneously) while the others served as untreated controls. Rats in both groups were killed in groups of 6 at intervals of 5 days and the re-innervation of the tibialis anterior muscle was examined histologically using the bromoindigo-silver method. Neuromuscular re-innervation was first apparent 15 days post-operatively and was largely complete by the 35th day in the T3-treated group. In the untreated control animals only two thirds of the end-plates were innervated after 35 days. The argyrophilic remains of degenerated axons disappeared more quickly in rats treated with T3, and degenerative changes in the structure of the subneural apparatus were less severe in these animals than in the controls. It is suggested that consideration be given to the possibility of using exogenous T3 in the clinical management of human peripheral nerve injuries.