Sodium dependency of [3H]imipramine binding in rat cerebral cortex.

[3H]imipramine binding to membranes prepared from rat brain cortex is sensitive to sodium ions. The dissociation constant, K(D), in the absence of added sodium was four times greater than in the presence of 120 mM sodium chloride. There was no change in the maximal binding, Bmax, of [3H] imipramine binding in the absence of sodium. The addition of Tris chloride in the range of 10-300 mM caused only a small decrease in the binding of [3H] imipramine whereas the addition of similar concentrations of sodium chloride increased linearly the binding of [3H] imipramine at 1 nM by over 100%.