[Existence of phencyclidine receptor in guinea pig atria].

[3H]-PCP was used in receptor binding studies on membrane preparation from guinea pig atria. It was found that this binding was specific, saturable, reversible and stereoselective. Scatchard plots revealed that guinea pig atria had two different affinity binding sites. The high affinity constant (Kd1) and low affinity constant (Kd2) were 12.15 +/- 0.414 nmol/l and 561.23 +/- 121.36 nmol/l, respectively; the maximum bindings (Bmax) were 0.71 +/- 0.029 pmol/mg protein (Bmax1) and 1.047 +/- 0.099 pmol/mg protein (Bmax2), respectively. The displacement analysis revealed that the [3H]-PCP binding was inhibited by the ligands of both PCP and sigma receptors, while the inhibition of PCP ligands was larger than of sigma ligands. Etorphine, an agonist of opioid receptors, failed to inhibit the binding of [3H]-PCP. The results mentioned above show the existence of a specific PCP receptor in guinea pig atria. The autoradiographic analysis of guinea pig right atria was shown that there was autoradiographic localization of [3H]-PCP on atria of guinea pig with homogeneous distribution, suggesting that the distribution of PCP receptor in atria was homogeneous relatively.