FUNCTIONAL PROJECTION OF SENSORY LATERAL PLANTAR AND SUPERFICIAL PERONEAL NERVE AXONS TO GLABROUS AND HAIRY SKIN OF THE RAT HINDFOOT AFTER SCIATIC-NERVE LESIONS

The functional regeneration of C-fibers mediating polymodal nociceptio n and low-threshold mechanoreceptive axons in the lateral plantar nerv e (LPN) and the foot branch of the superficial peroneal nerve (fSPN) w as evaluated in normal rats and 3 months after unilateral sciatic nerv e crush or neurotomy and suture. The area covered by low threshold mec hanoreceptors (LTMs) was tested through gentle mechanical skin stimula tion and recording from the relevant nerve. In regenerated animals the glabrous skin area with functional LPN-related LTMs was severely redu ced following a crush lesion. Functional receptors of that type were a bsent after neurotomy and suture, The hairy skin area with fSPN-relate d LTMs was smaller than normal, particularly following neurotomy and s uture. The distribution of polymodal C-fibers was tested through stimu lation-induced extravasation of Evans blue albumin (EBA). In the glabr ous LPN skin domain the area showing EBA extravasation did not return to normal after any of the lesion types. However, in the hairy fSPN sk in area the distribution of EBA extravasation appeared largely normal following both injuries. We conclude that polymodal nociception reappe ars to a greater extent than low threshold mechanosensitivity, and tha t both modalities regenerate better in hairy skin than in glabrous ski n. (C) 1994 Academic Press, Inc.