Tectorial membrane I: Static mechanical properties in vivo

Although the tectorial membrane in the mammalian cochlea plays a crucial role in hair-cell stimulation, its mechanical properties have never been investigated under conditions approximating those under which it normally functions. For this reason, we performed such investigations in live Mongolian gerbils. Access to the tectorial membrane was gained through the lateral wall in the second cochlear turn. As far as possible, sodium ions were kept away from the tectorial membrane by avoiding injury to Reissner's membrane, relieving the perilymphatic pressure and rinsing the scala media with an isotonic KCl solution. The tectorial membrane was manipulated with a flexible micropipette in three, approximately orthogonal, directions. Under these conditions the membrane was found to be highly compliant and resilient and to have a relatively high tensile strength. Its viscosity was low. Some of these attributes were altered by sodium ions, dyes, or death.