Binding of [3H]substance P to putative substance P receptors in rat brain membranes

[3H]Substance P was used to label putative substance P receptors in rat brain membranes. [3H]Substance P binding was saturable, reversible, and displaceable by non-radioactive substance P. Association, dissociation and saturation experiments suggest a single site interaction of [3H]substance P to its binding site (k-1/k+1 = 0.56 nM; KD = 0.9 nM, Bmax 86.5 fmol/mg protein.