The ventral caudal nerve: a physiologic-morphometric study in three different rat strains.

The caudal nerve is often used for investigating alterations in nerve conduction velocity (NCV) to determine the presence of peripheral neuropathy in animal models. In the present study, the rat caudal nerve of two outbred strains (Wistar Hannover and Sprague-Dawley) and one inbred strain (Fischer-344) was analyzed with regard to morphologic, morphometric, and physiologic features. In all three strains, we calculated the myelinated fiber diameter, myelinated axon diameter, and g-ratio in the proximal caudal nerve and correlated these results with NCV in the distal caudal nerve. Although the caudal nerves were morphologically similar in the three rat strains, a significant difference was present morphometrically: there was a statistically significant increase in the g-ratio associated with a reduction in myelinated fiber diameter in Fischer-344 rats vs. Wistar Hannover and Sprague-Dawley animals (p < 0.01). However, there was no significant difference in NCV results in the distal caudal nerve. The present study adds morphologic and morphometric information on the rat caudal nerve that might be useful for a better interpretation of studies involving this nerve and its pathological changes in experimental models of peripheral neuropathies.