Adaptive bone modeling in the middle ear is substance-P dependent.

Hypothesis: Localized bone modeling in the middle ear is substance-P dependent.

Background: Processes of local bone modeling and remodeling in the middle and inner ear lead to destructive processes such as otosclerosis and chronic otitis media. The cellular events associated with these processes are known, but the mechanisms of the control and activation of the involved cells are not. The authors hypothesized that one of the control mechanisms of local bone modeling is related to the action of a neuropeptide, substance-P and that capsaicin, which depletes substance-P, would block modeling in the gerbil model of adaptive bone modeling.

Methods: One middle ear of each of 24 Mongolian gerbils was pressurized to 10 mmHg to induce adaptive bone modeling. Half of the animals were pretreated with capsaicin and half received vehicle alone. At the end of the 5-day experimental period, the bulla was studied histomorphometrically for osteoclastic and osteoblastic activity.

Results: Capsaicin pretreatment inhibited the percent of bone occupied by osteoclasts on the inner surface of the bulla and the rate of mineralization of bone on the outer surface of the bulla.

Conclusions: It is likely that substance-P is a mediator of localized adaptive bone modeling in vivo. Processes of bone modeling and remodeling in the middle and inner ear may be under neural control.