Regeneration of Specific Vibrissal Nerves

Rice, Frank

Abstract

Regeneration of transected nerves results in a loss of sensitivity, loss of sensory discrimination, and/or a variety of bizarre of inappropriate sensations. Little is known about the peripheral or central interactions that occur between different types of sensory afferents or between different fascicles within a transected nerve. The sensory innervation of the mystacial pad in the rat is systematically organized in such a way that subsets of sensory terminals are compartmentalized and are supplied by separate nerve branches from the infraorbital nerve. This organization permits surgical approaches to gain access to specific, repeatable superficial and deep vibrissal nerves that supply separate compartments within vibrissal follicle-simus complexes (f-SC's). These nerves can be selectively labeled with HRP to determine their brainstem projection sites via transganglionic transport. A partially completed study has demonstrated that the superficial and deep vibrissal nerves are separate and predictable projects sites.
The first aim of this proposal is to complete the analysis of the topographical organization of these projects. Deep vibrissal nerves can also be rerouted such that the regeneration (as seen in Winkelmann reduced silver preparations) can invade peripheral territories that normally belong to the superficial nerves.
The second aim of this proposal is to refine the surgical rerouting technique and to determine the conditions that result in no misguided regeneration.
The final aim of the proposed study is to combine the nerve rerouting experiments with the HRP transganglionic labeling experiments to determine the central connections of the misguided deep vibrissal nerves. The status of the peripheral regeneration will be assessed in Winkelmann preparations of the tampered F-SC's. In the same animals, the organization of the afferent projects to the brainstem will be assessed by transganglionic transport of HRP from the regeneration nerves. The experiments will determine if afferents that have regenerated to the incorrect local targets in the periphery can sprout into appropriate central target or it the central projects remain unchanged. Finding the first result brainstem nuclei would remain subject to inappropriate inputs.