Regeneration in botulinum-poisoned forelimbs of the newt, Triturus

Regeneration of an amputated limb will take place in the salamander provided that an adequate nerve supply is present in the stump. It has been suggested that acetylcholine (ACh) released by the nerves may be the neural trophic factor which enables regeneration to take place. In order to test this hypothesis we amputated the limbs of Triturus viridescens and then administered high systemic doses of botulinum toxin. The purified toxin is the most highly specific and potent cholinergic blocking agent known. In spite of effective cholinergic blockade, regeneration of the amputated limbs took place, and proceeded at a normal rate. It is concluded that ACh is not necessary for limb regeneration to occur, and therefore does not fulfill the role of a neurotrophic agent in this situation. However, this does not rule out the possibility that ACh may be the sole neurotrophic agent, or associated with the agent, in other biological systems such as skeletal muscle.