Regrowth of cholinergic and catecholaminergic neurons along a peripheral and central nervous pathway

The transitional region between the peripheral and central nervous system in lumbosacral dorsal roots of rats were used in order to test the regeneration capacity of neurons with different metabolic characteristics. Ventral root fibres (cholinergic) and hypogastric nerve fibres (catecholaminergic) were coapted to the central stump of cut lumbosacral dorsal roots and permitted to regrow along the peripheral nervous and central nervous parts of the dorsal root. After a postoperative period of 1.5-9 months the animals were sacrificed and the coapted nerves and roots were investigated by histochemistry, light and electron microscopy. Regrowth of both cholinergic and catecholaminergic neurons had occurred into the peripheral nervous part of the root. In the central nervous part of the root, regeneration was abortive for both types of neurons. The astrocytes of the central nervous part of the root showed different morphological features according to the type of neuron that had been coapted to the dorsal root. The results are discussed in terms of neurotropism, neuron target dependence, microenvironment and type of regenerating neuron.