SUBSTANCE P-RELATED AND CALCITONIN-GENE-RELATED PEPTIDE-IMMUNOFLUORESCENT NERVES IN THE REPAIR OF EXPERIMENTAL BONE DEFECTS

Healing of an experimental bony defect in the rat's tibia was studied with an immunofluorescent technique to clarify when and where substanc e P (SP) and calcitonin gene-related peptide (CGRP) would develop. The normal tibia showed a few SP- and CGRP-immunofluorescent nerve fibres . In the experimental tibia, the number of these fibres increased on t he 6th day after operation, reached a peak of proliferation on the 15t h day and reverted to normal after the 24th day. The changes were asso ciated with the development and decay of callus tissue suggesting that harmful stimuli from the injured site in a bone could be mediated by sensory nerves throughout the repair period. Most of the SP- and CGRP- immunofluorescence was seen near the vessels, frequently in the same n erve fibres. The SP- and CGRP-immunofluorescent nerves seemed to take part jointly in callus formation through the enhancement of local bloo d flow.