We investigated the effects of gadolinium ion (Gd3+) on the mechano-electrical transduction (MET) current using a whole-cell patch electrode voltage clamp technique in dissociated cochlear hair cells of chicks. Gd3+ blocked the MET channel in a concentration- and voltage-dependent manner. At -50 mV, Gd3+ blocked the MET channel, with a Hill coefficient of 1.14 and a dissociation constant (KD) of 1.01 x 10(-5) M. Adaptation of the MET current disappeared after the introduction of Gd3+, a change that may be due to a decrease in inward going MET currents, specifically the Ca2+ component.