Role of Nerves - Regeneration
It has been seen that soon after amputation nerves invade the regeneration blastema. If the stump is denervated by cutting the nerves supplying the limb as they come out from the spinal cord, and are avoid from regrowing into the site of amputation them regeneration fails to take place. The apical cap is not formed. In larval urodeles, denervation results in large scale regression of stump tissues and the whole limb stump may disappear. If the nerve fibers are allowed to regrow into the stump earlier than a thick skin forms on the wound surface regeneration may be re-initiated. These studies have displayed with certainty that the existence of nerves is essential for regeneration of the limb.
A number of experimental studies have been made to know the nature and mechanism of nerve influence on limb regeneration in urodeles. The nerves are believed to generate a "trophic influence" on the blastema cells of the regenerating limb. This neurotrophic effect has been emerge to be produced by all nerves, if motor or sensory or central irrespective of whether they have functional relationship with the central nervous system or not. Grafting of spinal ganglia in the regenerating area of limbs, whose own nerves have been cut and severed, also promote regeneration. Though, it has been found that the presence of a minimum number of nerve fibers is essential for regeneration. Below this threshold regeneration does not take place.