Binding parameters for σ₁ receptors in the absence and presence of dextromethorphan.

Saturation binding assays in brain homogenates for σ1 receptors were conducted using [3H](+)-pentazocine as the radioligand. The assays were performed in the absence or presence of dextromethorphan (400 nM). The Kd and Bmax were determined using nonlinear regression. Dextromethorphan produced a significant decrease in Kd and Bmax. Data shown are expressed as mean ± S.E.M. aP<0.05, compared with [3H](+)-pentazocine alone; paired t-test.