Computational NeuroscienceInnervation mapping of the hind paw of the rat using Evans Blue extravasation, Optical Surface Mapping and CASAM

- Evans Blue technology, OSM and CASAM analysis represents an excellent tool to examine the origin of the nerves that supplies the skin in detail.
- Evans Blue extravasation on the skin of rats corresponds exactly to the innervation area of the stimulated nerve.
- Evans Blue extravasation was absent on the footpads of the rats' hind paw.
- Larger areas of overlap were seen on the dorsal part of the hind paw in comparison to plantar side of the hind paw.

BackgroundAlthough numerous studies investigate sensory regeneration and reinnervation of the hind paw of the rat after nerve damage, no comprehensive overview of its normal innervation is present in literature. The Evans Blue extravasation technique is a well-known technique to study patterns of skin innervation. This technique has been performed differently by various groups but was never used to study the entire skin innervation in rats' hind paw including all three branches of the sciatic nerve and the saphenous nerve in detail.New methodIn this paper, we have used the Evans Blue extravasation technique to chart the skin areas innervated by the sural, peroneal, tibial and/or saphenous nerves, which together innervate the entire hind paw of the rat, and use a new technique to analyze the distribution, overlap and variability of the results. The technique is based on analysis of whole hind paws using Optical Surface Mapping (OSM) in combination with the Computer Assisted Surgical Anatomy Mapping (CASAM) technology.ResultsWhile the plantar hind paw is mainly innervated by the tibial nerve, the dorsal hind paw is supplied by the sural, peroneal and the saphenous nerve.Comparison with existing methodsAlthough our results basically concur with the general nerve-specific innervation of the rat hind paw, they show considerable detail in their areas of overlap as well as in the amount of variability between animals.ConclusionThese results will be invaluable to study and evaluate patterns of innervation and reinnervation of intact and damaged nerve fibers.