EXPRESSION OF G-ALPHA PROTEINS IN THE DEVELOPING, DENERVATED, OR INJURED RAT MOLAR TOOTH

The purpose of this study was to map the distribution of alpha-subunit s of G-proteins - G alpha(olf s), G alpha(olf), G alpha(s), G alpha(i) , G alpha(o), G alpha(z) and G alpha(qll) - in developing, denervated or injured rat molar teeth, using fluorescence microscopic immunohisto chemistry coupled with immunogold electron microscopic immunocytochemi stry. In rat fetuses (E17-E21), a widespread expression of Gag,, was s een in maxillary/mandibular mesenchyme as well as in developing teeth. In addition, intensely G alpha(o)-positive nerve fibers were associat ed with the dental epithelium and the dental papilla of developing tee th. Other G proteins were absent or sparsely distributed during early tooth development. In the adult tooth pulp, odontoblasts appeared to e xpress mainly G alpha(olf s), G alpha(o), and G alpha(qll). Nerve fibe rs were immunoreactive to G alpha(i), G alpha(o) and G alpha(z). In ad dition, pulpal blood Vessels expressed varying levels of G alpha(olf s ), G alpha(z) and G alpha(qll) while G alpha(olf s), G alpha(olf), G a lpha(o) and G alpha(qll) were found in various pulpal mesenchymal cell s. After adult denervation, nerve fiber-related G-protein immunoreacti vity disappeared, but no other changes in pulpal G-protein immunoreact ivity were noted. Odontoblasts and mesenchyme cells were intensely G a lpha(i)-positive underneath a pulpal traumatic exposure, indicating an injury-induced pulpal upregulation of G alpha(i). The findings that G alpha(i), G alpha(o) and G alpha(z) are expressed in pulpal sensory n erve fibers suggest that these G proteins participate in signal convey ance from the target to the trigeminal nerve cell body.