Single ion channel currents in neuropile glial cells of the leech central nervous system

Abstract

The patch-clamp technique was used to investigate the activity of single ion channels in neuropile glial (NG) cells in the central nervous system (CNS) of the medicinal leech, Hirudo medicinalis. We found evidence for two distinct Cl- channels that could be distinguished by their basic electrical properties and their responses to different inhibitors on single ion channel currents. In the inside-out configuration in symmetrical Cl- solutions, these channels showed current-voltage relationships with slight outward rectification, mean conductances of 70 and 80 pS, and reversal potentials near 0 mV. Significant permeability to Na+, K+, or SO4(2-) could not be detected. The open-state probability of the 70 pS Cl- channel increased with membrane depolarization, whereas the open-state probability of the 80 pS Cl- channel was voltage-independent. The application of the stilbene derivative DIDS (100 microM) to the cytoplasmic side of the glial cell membrane blocked both Cl- channels. The activity of the 70 pS channel was blocked irreversibly by DIDS, whereas the activity of the 80 pS channel reappeared after wash-out of DIDS. Both channels were blocked reversibly by 1 mM Zn2+. K+ channels could only be observed occasionally in the soma membrane of the NG cells. We have characterized a 60 pS K+ channel with a high selectivity for K+ over Na+. The low density of K+ channels in the soma membrane may indicate a non-uniform distribution of this channel type in NG cells.

In vitro synthesis and oligomerization of the mechanosensitive channel of large conductance, MscL, into a functional ion channel

“…The bilayer set‐up consists of two chambers connected by a 150 μm aperture through a Delrin cup. Painted planar bilayers were formed in the aperture from a 10 mg/ml n ‐decane solution of PE:PC (7:3, w/w) as described [13,14]. The cup was placed in a black Delrin chamber and filled with 1 ml bilayer buffer (150 mM NaCl, 8 mM HEPES, pH 7.5).…”

Effects of ATP and derivatives on neuropile glial cells of the leech central nervous system

“…Their dissection as well as the isolation of the ganglia was done as described by Schlue and Deitmer (1980). After isolation of the ganglia, the neuropile glial cells were exposed by removing the ventral part of the outer ganglion capsule and the ventral neuronal somata (Mü ller et al, 1993).…”