Dopamine receptors expressed in the Xenopus oocytes injected with bovine striatal mRNA.

The response to dopamine (DA) of Xenopus oocytes injected with bovine striatal mRNA was electrophysiologically and pharmacologically investigated under a voltage-clamped condition. In oocytes injected with bovine striatal mRNA and then treated with collagenase (denuded oocytes), DA applied by superfusion dose-dependently induced oscillatory inward currents with a long latency and an ED50 value of 12.0 microM. mRNA non-injected denuded oocytes did not respond to DA up to concentrations of 1 mM. The reversal potential of DA-induced currents was about -25 mV, indicating that DA increased a Cl(-)-conductance. DA-induced currents were easily desensitized by repeated applications of DA. Haloperidol and SCH-23390 abolished DA-induced currents, while propranolol and mianserin showed no effect. Furthermore, SK&F-38393, a specific agonist of the DA D1 receptor, induced similar oscillatory currents as DA did. These results suggest the possibility that functional D1 and D2 DA receptors were co-expressed in Xenopus oocytes by injection of bovine striatal mRNA.