VOLTAGE-EVOKED AND GABA-EVOKED CURRENTS FROM MULLER GLIAL-CELLS OF THE BABOON RETINA

THE electrophysiological features of isolated baboon Muller cells was investigated using the whole-cell voltage-clamp technique. Application of depolarizing voltage steps evoked transient inward and delayed out ward currents. The transient currents disappeared when extracellular N a+ was replaced by choline(+) and were substantially decreased by appl ication of tetrodotoxin (1 mu M). The outward currents were strongly d iminished by extracellular Ba2+ (1 mM), and the hyperpolarization-gene rated inward currents disappeared following application of Ba2+. The r ecently described gamma-aminobutyric acid A (GABA(A)) receptor current s were increased by flunitrazepam, nordiazepam, pentobarbital and Zn2, as well as by the inverse agonist DMCM. These results suggest that t he baboon Muller cells possess the same voltage-dependent current patt ern as those from other species, e.g. humans, whereas their GABA(A) re ceptors react in an uncharacteristic manner to DMCM and Zn2(+), when c ompared with neuronal GABA(A) receptors.