Neural nature of the time-dependent factor(s) involved in motor reinnervation

The influence of a time interval between nerve transection and reimplantation into a foreign muscle on the effectiveness of reinnervation was studied in the rat. We evaluated the weight loss and the maximal twitch and tetanic tensions developed by the reinnervated muscle upon nerve stimulation 60 days after reimplantation (i) of an acutely severed nerve onto an acutely denervated muscle; (ii) of a chronically (20 days) severed nerve onto an acutely denervated muscle, and (iii) of an acutely severed nerve onto a chronically denervated muscle. The best recovery was obtained when a chronically severed nerve was implanted into an acutely denervated muscle. We conclude that a neural time-dependent factor(s) is involved in motor reinnervation.