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Plasticity of primary afferent acid phosphatase expression following rerouting of afferents from muscle to skin in the adult rat
Author(s) -
McMahon Stephen B.,
Moore Christopher E. G.
Publication year - 1988
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.902740102
Subject(s) - reinnervation , anatomy , sural nerve , biology , axotomy , spinal cord , gastrocnemius muscle , anastomosis , central nervous system , medicine , endocrinology , skeletal muscle , neuroscience , psychiatry
We have examined the possibility that reinnervation of a new peripheral target by primary afferent neurones can alter the histochemical properties of those afferents in the adult rat. The hindlimb sural and gastrocnemius nerves largely supply skin and muscle, respectively. In adult animals these nerves were cut and rejoined to either their own distal stumps (self‐anastomosis) or that of the other nerve (cross‐anastomosis) and allowed to regenerate for 12‐16 weeks to reinnervate an appropriate or inappropriate target. Fluoride‐resistant acid phosphatase (FRAP) is a chemical marker found in many unmyelinated afferents. We have determined the FRAP expression in normal and regrown nerves and examined its distribution in the dorsal horn of animals with self‐ and cross‐anastomosed nerves. While normal and self‐anastomosed sural nerves stained heavily for FRAP, gastrocnemius nerves showed either no staining or only the occasional fibre. Cross‐anastomosed gastrocnemius nerves, now innervating the skin, showed a significant increase in staining, in some cases approaching the levels normally seen in sural nerves. Conversely, cross‐anastomosed sural nerves (innervating muscle) showed decreased FRAP staining. In the normal dorsal horn the terminals of FRAP containing afferents form a thin band extending throughout the mediolateral extent of lamina II (Devor and Claman: Brain Res. 190: 17‐28, '80). One week after axotomy of the sural nerve, FRAP is depleted from its terminals and a gap appears in the normal FRAP staining pattern in the lumbar enlargement of the spinal cord. The new expression of FRAP in cross‐anastomosed nerves was also seen in their terminals in the dorsal horn. This occurred in lamina II of the spinal segments L4‐L6 and was quantified by measuring the size of the gap in FRAP staining produced by sural axotomy. Cross‐anastomosis of the gastrocnemius nerve reduced the size of the gap significantly to 69 ± 7.8% (standard error) of the gap seen contralaterally with self‐anastomosis. The results demonstrate that reinnervation of an inappropriate target can lead to changes in the histochemical properties of afferents in adult animals. It is suggested that tissue‐specific trophic factors produced by the target tissues are sampled by innervating neurones and act to modify their properties.