Microscopic anatomy of the sural nerve in the postnatal developing rat: a longitudinal and lateral symmetry study.

Rat sural nerve is widely used in experimental studies investigating injury and regeneration of the peripheral nervous system. However, it has not yet been established whether morphological and morphometric parameters differ within corresponding levels of the rat sural nerve. The aims of the present study were to investigate the normal morphological and morphometric aspects of the sural nerve in postnatal developing female rats, with special attention to longitudinal morphology and lateral symmetry. Rats aged 30, 90 and 180 days were killed, and proximal and distal segments of the right and left sural nerves were prepared for light microscopy and morphometric study. No differences were found between the proximal and distal segments or between the right and left sides at the same levels. In addition, postnatal growth continuously and symmetrically affected the sural nerve fascicles and myelinated fibres. Fibre population distribution was also affected by increasing body weight; distribution was unimodal at 30 days, and by 180 days this distribution was established as bimodal. We concluded that the sural nerve is long and constant in its morphology and presents a continuous and symmetrical growth, more pronounced between 30 and 90 days of age, thus providing a good model for experimental neuropathies.