Sprouting and functional regeneration of an identified neuron in Helisoma.

A pair of identified neurons in the snail, Helisoma, rapidly regenerate after severance of their axons and functionally reinnervate their former target organs, the salivary glands. Functional reinnervation occurred in 40% of the preparations within 6 days and in 93% of those examined on or after day 7 following axon severance. Neuronal regeneration is highly specific. For instance, in each case in which the salivary glands were found to be reinnervated and simultaneous records were taken from gland cells and their normal effector neuron, this neuron (neuron no. 4) was found to have reinnervated the glands. In addition, regeneration following total denervation of the feeding musculature can result in feeding movements which appear normal on visual inspection and by myographic recordins. Neural regeneration is manifested by extensive axonal sprouting. The site of initiation of sprouts is a function of the crush site, but sprouting is not totally restricted to the vicinity of the crush. In addition, the initial regeneration and axonal sprouting following severance of these axons is not dependent upon the presence of their original target organs.