The Journal of Neurophysiology Vol. 84 No. 6 December 2000, pp. 2975-2983
Copyright ©2000 by the American Physiological Society

Developmental Regulation of Calcium Channel-Mediated Currents in Retinal Glial (Müller) Cells

Department of Neurophysiology, Paul Flechsig Institute of Brain Research, University of Leipzig, D-04109 Leipzig, Germany

Bringmann, A., S. Schopf, and A. Reichenbach. Developmental Regulation of Calcium Channel-Mediated Currents in Retinal Glial (Müller) Cells. J. Neurophysiol. 84: 2975-2983, 2000. Whole cell voltage-clamp recordings of freshly isolated cells were used to study changes in the currents through voltage-gated Ca²⁺ channels during the postnatal development of immature radial glial cells into Müller cells of the rabbit retina. Using Ba²⁺ or Ca²⁺ ions as charge carriers, currents through transient low-voltage-activated (LVA) Ca²⁺ channels were recorded in cells from early postnatal stages, with an activation threshold at 60 mV and a peak current at 25 mV. To increase the amplitude of currents through Ca²⁺ channels, Na⁺ ions were used as the main charge carriers, and currents were recorded in divalent cation-free bath solutions. Currents through transient LVA Ca²⁺ channels were found in all radial glial cells from retinae between postnatal days 2 and 37. The currents activated at potentials positive to 80 mV and displayed a maximum at 40 mV. The amplitude of LVA currents increased during the first postnatal week; after postnatal day 6, the amplitude remained virtually constant. The density of LVA currents was highest at early postnatal days (days 2-5: 13 pA/pF) and decreased to a stable, moderate level within the first three postnatal weeks (3 pA/pF). A significant expression of currents through sustained, high-voltage-activated Ca²⁺ channels was found after the third postnatal week in ~25% of the investigated cells. The early and sole expression of transient currents at high-density may suggest that LVA Ca²⁺ channels are involved in early developmental processes of rabbit Müller cells.