CHARACTERIZATION OF THE SPECIFIC BINDING OF THE HISTAMINE H-3 RECEPTOR ANTAGONIST RADIOLIGAND [H-3] GR168320

We have examined the specific binding of the tritiated derivative of t he potent histamine H-3 receptor antagonist, H-imidazol-4-yl)-piperidi n-1-yl]iminomethyl}-amine ([H-3]GR168320), to homogenates of rat cereb ral cortex. Specific binding of [H-3]GR168320 at 37 degrees C associat ed and dissociated rapidly. Binding was saturable( B-max 412 +/- 89 fm ol/mg protein) and of high affinity (K-d 0.12 +/- 0.11 nM). Saturation studies suggested the involvement of a single site. Histamine H-3 rec eptor agonists and antagonists inhibited [H-3]GR168320 binding with hi gh affinity. Agonist and antagonist affinities correlated when compare d with affinities obtained using the tritiated histamine H-3 agonist r adioligand N-alpha-methylhistamine.