PROPERTIES OF VOLTAGE-ACTIVATED NA-CELLS IN-SITU AND AFTER ACUTE ISOLATION FROM TISSUE-SLICES( AND K+ CURRENTS IN MOUSE HIPPOCAMPAL GLIAL)

In the present study, we were interested in a quantitative analysis of voltage-activated channels in a subpopulation of hippocampal glial ce lls, termed ''complex'' cells. The patch-clamp technique in the whole- cell mode was applied to identified cells in situ and to glial cells a cutely isolated from tissue slices. The outward current was composed o f two components: a sustained and a transient current. The transient K + channel had electrophysiological and pharmacological properties rese mbling those of the channel through which the A-currents pass. In addi tion, this glial A-type current possessed a significant Ca2+ dependenc e. The current parameters determined in situ or in isolated cells corr esponded well. Due to space clamp problems in situ, properties of volt age-dependent Naf currents were only analysed in suspended glial cells . The tetrodotoxin (TTX) sensitivity and the stationary and kinetic ch aracteristics of this current were similar to corresponding properties of hippocampal neurons. These quantitative data demonstrate that at a n early postnatal stage of central nervous system maturation, glial ce lls in situ express a complex pattern of voltage-gated ion channels. T he re suits are compared to findings in other preparations and the pos sible consequences of transmitter-mediated channel modulation in glial cells are discussed.