EFFECTS OF ADENOSINE ON CHICK RETINAL-PIGMENT EPITHELIUM - MEMBRANE-POTENTIALS AND LIGHT-EVOKED RESPONSES

We examined the effects of adenosine, a putative mediator of neuroprot ection during cerebral ischemia, on the electrophysiological character istics of retina-retinal pigment epithelium-choroid preparations obtai ned from 1-7 day-old chick and maintained in vitro. Our experiments pr oduced the following results. First, superfusion of the retinal surfac e with adenosine (0.1 mM) increased the trans-tissue potential. The tr ans-epithelial (but not the trans-retinal) potential was also increase d to the same magnitude with a time-course similar to that of the tran s-tissue potential. Second, adenosine produced a depolarization of the epithelial basal plasma membrane with a concomitant decrease in its b asal membrane resistance. Third, the trans-epithelial (but not the tra ns-retinal) c-wave in response to a light stimulus was augmented by ad enosine. Adenosine reduced the hyperpolarization of the epithelial bas al membrane, but had no effect on the extracellular concentration of K + in the subretinal region. Fourth, the light-peak that was elicited w ith a 300 s light stimulus was also depressed by adenosine. Fifth, whe n 4,4'-diisothiocy anostilbene-2,2'-disulfonate (DIDS), a relatively s elective inhibitor of Cl- channels, was perfused at 50 mu M on the cho roidal surface, adenosine-induced increases in the trans-tissue potent ial and the c-wave were both abolished. These results suggest that ade nosine increased the Cl(-)conductance of the basal plasma membrane of the retinal pigment epithelium and thereby augmented the standing pote ntial as well as the light-elicited membrane potentials of the retinal pigment epithelium, which seems to be involved in the pathophysiology of retinal ischemia.