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Archive » 1998 » 2 » | Archive » Medical field » Fields » Neurology » Archive » Medical field » Fields » Pathophysiology » Archive » Medical field » Research papers » Preclinical research paper »

Induction of collateral sprouting of sensory axons in the rat

 
Abstract:

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Collateral sprouting of axons in the pe­ripheral nervous system is a branching out­growth of new axon terminals from non-injured axons into adjacent denervated regions of tar­get tissue. The initiation of collateral sprouting is probably triggered by the interaction between the factors released by degenerated neural pathways or denervated target tissue, and pu­tative interaction between the injured and non­injured neurons within a dorsal root ganglion (transneuronal mechanism). Sprouting of axons along the neurilemmal tubes of Schwann cells was investigated by an end-to-side anastomo­sis of a peroneal nerve segment to the intact su­ral nerve on the hind limb of the rat. In group A, the peroneal nerve segment from the contrala­teral limb was attached to the sural nerve. No­ne of the nerves on the side of the anastomosis were injured. In group B, the same procedure was used as in group A. In addition, dorso-cutaneous nerves from the L4–L6 spinal segments were cut. Injured neurons were therefore present in the dorsal root ganglia from which axons of the sural nerve arise. The skin of the limb was not denervated. In group C, an end-to-side ana­stomosis of the peroneal nerve segment from the ipsilateral limb was made on the sural ner­ve. On the same limb, the saphenus nerve was cut and ligated. The skin around the terminal in­nervation field of the sural nerve was therefore denervated. The growth of sensory axon sprouts into the anastomosed nerve segments was mo­nitored by the nerve-pinch test. In addition, the number of myelinated axons in the anastomosed nerve cross-sections was counted. Eight weeks after surgery the nerve-pinch test showed no sprouting of the sural nerve into the anasto­mosed nerve segments of the peroneal nerve in any animal in group A. In contrast, we detected sprouting in all group C animals and in four out of five animals in group B. We found only few myelinated fibres in the anastomosed peroneal nerves in group A. This was statistically signifi­cantly less than in groups B and C (p < 0.05). Mye­linated fibres in the anastomosed peroneal nerve in group B significantly outnumbered those in group C (p < 0.02). We found out that collateral sprouting cannot be induced by Schwann cell tu­bes alone, but rather denervated target tissue or transneuronal mechanisms are needed to induce the process. Transneuronal mechanism is an im­portant factor stimulating the initiation of colla­teral sprouting.

Authors:
Pavčnik Maja, Kovačič Uroš

Keywords:
axons, nerve degeneration, nerve regeneration, peroneal nerve, sural nerve, rats

Cite as:
Med Razgl. 1998; 37: 173–90.

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