IMMUNOHISTOCHEMICAL AND ELECTRON-MICROSCOPIC DEMONSTRATION OF NERVE-FIBERS IN RELATION TO GINGIVA, TOOTH GERMS AND FUNCTIONAL TEETH IN THE LOWER JAW OF THE CICHLID TILAPIA-MARIAE

Immunohistochemistry revealed the presence of numerous neurofilament ( NF)-like immunoreactive axons in relation to gingiva and dental follic les surrounding mineralizing tooth germs. The gingival nerve fibres fr equently approached the prospective papilla of early tooth primordia. Electron microscopic (EM) analysis revealed the presence of bundles of unmyelinated axons immediately below the epithelial-proprial junction of the gingiva. Bundles of nerve fibres were also present in the bord er zone between the prospective papilla of bud-stage tooth germs and s urrounding mesenchyme and in close proximity to blood vessels of the f ollicles surrounding older tooth germs, but no axons were observed wit hin the emerging dental papilla. In the individual functional tooth, a bundle of NF-like immunoreactive nerve fibres entered the apical part of the pulp forming a subodontoblastic plexus at mid-pulpal levels. E M analysis showed that the apical bundle consisted of many unmyelinate d and a few myelinated axons invested by Schwann cell processes. The s ubodontoblastic plexus contained unmyelinated axons only. Thin, axon-l ike profiles were also seen in predentinal tubules. Nerve fibres were not observed at pulpal horn levels and in the ligamentous attachment. It is concluded that both immature and mature parts of the lower-jaw d entition of the cichlid T. mariae are innervated and that the microsco pic anatomy of this innervation is partly similar to the pattern seen in developing and adult mammals.