Expression of Galpha proteins in the developing, denervated, or injured rat molar tooth

The purpose of this study was to map the distribution of alpha-subunits of G-proteins--Galpha(olf s), Galpha(olf), Galpha(s), Galpha(i), Galpha(o), Galpha(z) and Galpha(q11)--in developing, denervated or injured rat molar teeth, using fluorescence microscopic immunohistochemistry coupled with immunogold electron microscopic immunocytochemistry. In rat fetuses (E17-E21), a widespread expression of Galpha(q11) was seen in maxillary/mandibular mesenchyme as well as in developing teeth. In addition, intensely Galpha(o)-positive nerve fibers were associated with the dental epithelium and the dental papilla of developing teeth. Other G proteins were absent or sparsely distributed during early tooth development. In the adult tooth pulp, odontoblasts appeared to express mainly Galpha(olf s), Galpha(o), and Galpha(q11). Nerve fibers were immunoreactive to Galpha(i), Galpha(o) and Galpha(z). In addition, pulpal blood vessels expressed varying levels of Galpha(olf s) Galpha(z) and Galpha(q11) while Galpha(olf s), Galpha(olf), Galpha(o) and Galpha(q11) were found in various pulpal mesenchymal cells. After adult denervation, nerve fiber-related G-protein immunoreactivity disappeared, but no other changes in pulpal G-protein immunoreactivity were noted. Odontoblasts and mesenchyme cells were intensely Galpha(i)-positive underneath a pulpal traumatic exposure, indicating an injury-induced pulpal upregulation of Galpha(i). The findings that Galpha(i), Galpha(o) and Galpha(z) are expressed in pulpal sensory nerve fibers suggest that these G proteins participate in signal conveyance from the target to the trigeminal nerve cell body.