SENSORY AND MOTOR DENERVATION INFLUENCE EPIDERMAL THICKNESS IN RAT FOOT GLABROUS SKIN

Denervation in man often results in shiny, dry,thin skin. A previous s tudy has shown that the epidermis of glabrous skin in the rat becomes approximately 40% thinner within 1 week following sciatic nerve transe ction, but which nerve fiber type or types influence epidermal thickne ss is unknown, In this study, we compared the effects on the epidermis of selective sensory, motor, and sympathetic denervation. Protein gen e product 9.5 and calcitonin gene-related peptide immunocytochemical s taining were used to determine the extent of denervation of epidermis, dermis, and sweat glands in the footpads. Epidermal thickness of the glabrous plantar skin of the foot was measured, To verify the specific ity and reliability of each animal model, the relevant regions of the peripheral nervous system were examined by light or electron microscop y or both. Epidermal thickness decreased significantly following sciat ic nerve transection (58% of control, P < 0.05) and dorsal root gangli onectomy (59%; P < 0.05), The thickness also decreased following lumba r ventral rhizotomy (61%; P < 0.01), destruction of lumbar spinal moto r neurons (66%; P < 0.05), and botulinum toxin-induced paralysis of th e tibialis anterior and gastrocnemius muscles (70%; P < 0.05). A sligh t decrease followed dorsal, rhizotomy (84%; P < 0.01). In contrast, no significant alterations in epidermal thickness were detected followin g sham operation and sympathectomy. Epidermal thinning was paralleled by reductions in the amounts of transcripts for glyceraldehyde-3-phosp hate dehydrogenase and beta-actin. These results suggest that selectiv e loss of both sensory and motor fibers to the hind limb can contribut e to reducing epidermal thickness in rat foot glabrous skin. (C) 1997 Academic Press.