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Specific paucity of unmyelinated C‐fibers in cutaneous peripheral nerves of the African naked‐mole rat: Comparative analysis using six species of bathyergidae
Author(s) -
Smith Ewan S,
Purfürst Bettina,
Grigoryan Tamara,
Park Thomas J.,
Bennett Nigel C.,
Lewin Gary R.
Publication year - 2012
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.23133
Subject(s) - biology , anatomy , mole , nerve fiber , peripheral nervous system , peripheral , endocrinology , medicine , central nervous system , biochemistry
In mammalian peripheral nerves, unmyelinated C‐fibers usually outnumber myelinated A‐fibers. By using transmission electron microscopy, we recently showed that the saphenous nerve of the naked mole‐rat ( Heterocephalus glaber ) has a C‐fiber deficit manifested as a substantially lower C:A‐fiber ratio compared with other mammals. Here we determined the uniqueness of this C‐fiber deficit by performing a quantitative anatomical analysis of several peripheral nerves in five further members of the Bathyergidae mole‐rat family: silvery ( Heliophobius argenteocinereus ), giant ( Fukomys mechowii ), Damaraland ( Fukomys damarensis ), Mashona ( Fukomys darlingi ), and Natal ( Cryptomys hottentotus natalensis ) mole‐rats. In the largely cutaneous saphenous and sural nerves, the naked mole‐rat had the lowest C:A‐fiber ratio (∼1.5:1 compared with ∼3:1), whereas, in nerves innervating both skin and muscle (common peroneal and tibial) or just muscle (lateral/medial gastrocnemius), this pattern was mostly absent. We asked whether lack of hair follicles alone accounts for the C‐fiber paucity by using as a model a mouse that loses virtually all its hair as a consequence of conditional deletion of the β‐catenin gene in the skin. These β‐catenin loss‐of function mice (β‐ cat LOF mice) displayed only a mild decrease in C:A‐fiber ratio compared with wild‐type mice (4.42 compared with 3.81). We suggest that the selective cutaneous C‐fiber deficit in the cutaneous nerves of naked mole‐rats is unlikely to be due primarily to lack of skin hair follicles. Possible mechanisms contributing to this unique peripheral nerve anatomy are discussed. J. Comp. Neurol. 520:2785–2803, 2012. © 2012 Wiley Periodicals, Inc.