Soluble Spiroperidol Binding Factors from Bovine Caudate Nucleus

Several properties of soluble spiroperidol binding factors separated from bovine caudate nucleus have been investigated by a previously unreported procedure. Data consistent with high particle weight and rapid binding equilibration are reported for high-affinity (+)butaclamol-sensitive components of a digitonin extract. A slower sedimenting component is found that also exhibits high affinity for spiroperidol but is not sensitive to (+)butaclamol. Centrifugation of a caudate nucleus homogenate yields a supernatant that appears to contain a component that exhibits spiroperidol binding that is more sensitive to displacement by (-) than by (+)butaclamol. The procedure used effects rapid separation of bound from unbound tritiated ligand on short columns of Sephadex G-15 followed by extrusion and sectioning of the Sephadex. The radioactivity remaining with each section is determined. The procedure is very rapid; the addition of active phases or the changing of the ionic environment, which may disturb the equilibrium, is avoided; and recovery of the protein free of bound ligand is easily affected.