Effects of guanethidine-induced sympathectomy on cell proliferation in the progenitive compartments of the neonatal mouse incisor.

Treatment of mice with guanethidine sulphate every 48 h from birth until 14 days produced a 64.2 and 68.0 per cent reduction in perikarya of the superior cervical and coeliac ganglia, respectively, at 15 days after birth and 78.9 and 81.3 per cent at 30 days. The growth rate of mice between 21 and 30 days after birth was significantly reduced. At 15 and 30 days after birth, C3H]-thymidine was injected into control and sympathectomized mice, and labelling indices for the inner enamel epithelium, outer enamel epithelium, stratum intermedium, stellate reticulum, odontoblasts, and pulp and periodontal ligament fibroblasts determined from autoradiographs. A statistically significant decline in labelhng index was found in the inner enamel epithelium, stellate reticulum, and odontoblast cell populations at 30 days as compared to 15 days in controls. Sympathectomized mice demonstrated a significant decline in labelling index in the inner enamel epithelium, stratum intermedium, odontoblasts, and pulp fibroblasts at 30 days as compared to 15 days. The sympathetic nervous system, therefore, has only a minimal role in regulation in incisor eruption and cellular proliferation. The effect of sympathectomy on the stratum intermedium and stellate reticulum may be due to increased tissue pressure resulting from loss of vasoconstrictive sympathetic control.