VOLTAGE-GATED CURRENTS IN RABBIT RETINAL ASTROCYTES

The voltage-gated currents of the astrocytes associated with the retin al capillaries of the rabbit retina were studied using whole-cell patc h clamp recording. The resting potential of these cells was -70 +/- 4. 8 mV (mean +/- SEM; n = 54), and the input resistance and cell capacit ance were 558 +/- 3.6 M Omega and 19.5 +/- 1.8 pF respectively. Depola rization to potentials positive to -50 mV evoked rapidly activating in ward and outward currents. The inward current was transient, eliminate d by substitution of choline for Na+ in the bathing solution, and redu ced by 50% in the presence of 1 mu M tetrodotoxin. The time-to-peak of the Na+ current was more than twice that for the Na+ current found in retinal neurons. The glial Na+ current was half-inactivated at -55 mV . A transient component of the outward K+ current was blocked by exter nal 4-aminopyridine while a more sustained component was blocked by ex ternal tetraethylammonium. At potentials between -150 and -50 mV the m embrane behaved Ohmically. Voltage-gated currents in retinal astrocyte s recorded in situ appear qualitatively similar to those described for some glial cells in vitro.