Effect of pharmacological sympathectomy on osteoclastic activity in the gerbilline auditory bulla in vivo

Bone destruction causes hearing loss in various middle ear disorders. The mechanisms of such pathological remodeling are unknown. Unilateral surgical sympathectomy is known to induce resorption within mandibular and auditory bulla bone. Explanation of the cause of this effect, however, may be confounded by hemodynamic changes induced by hemicranial sympathectomy and by uncertainty as to the neuroanatomical origins of sympathetic fibers. In this study, gerbils were infused with guanethidine sulfate (CS) to evaluate the in vivo effects of systemic sympatholysis on auditory bone remodeling. In addition, to discount any direct osteolytic effect, GS was assessed of its bone resorbing activity in vitro by means of the calvarial calcium release assay. The in vitro study revealed GS to have no effect on calcium release. The in vivo study revealed GS to increase both the osteoclast surface and number. Guanethidine-induced sympathectomy has thus been shown to increase remodeling in gerbilline auditory bone, while no direct osteolytic effect could be measured in vitro.