The influence of dopamine on active sodium transport across frog skin measured as short circuit current

The influence of dopamine (DA) on short circuit current (SCC) across isolated Rana esculenta skin was studied to determine whethera a DA receptor system exists in that cell membrane model and what is the influence of DA on SCC. Experiments were carried out with both alpha- and beta-adrenergic blockers and cocaine present in the Ringer solution. DA in cumulative doses added to the inner Ringer solution stimulated SCC in a dose-dependent manner. Apomorphine (10(-5) M) shifted the DA dose--response curve to the left and increased the maximum DA response. Haloperidol (10(-9) M) antagonized the effects of the DA depressing maximum response as well. Imidazole (10(-8) M and 10(-9) M) antagonized the influence of DA in a manner similar to haloperidol. It appeared that there were DA receptors in frog skin and that haloperidol as well as imidazole were DA antagonists which acted non-competitively.