Cockroach glial cell cultures: morphological development and voltage-gated potassium channels.
Insect glial cells derived from the embryonic brain of Periplaneta americana cockroaches have been kept in primary culture conditions for up to 3 weeks. Under the culture conditions used, the glial cells differentiated and formed a complex cellular network on the floor of the culture vessels from which glial-glial and glial-neuronal contacts could be seen. Single-channel currents from cell-attached glial membrane patches were recorded using the gigaseal technique. Depolarisation of membrane patches activated outward currents, which were abolished in the presence of extracellular 50 mM tetraethylammonium or 5 mM 4-aminopyridine, and were insensitive to 1 microM tetrodotoxin, 10 microM picrotoxin and 2 mM Cd2+. The amplitude of the outward currents increased linearly with depolarisation, and amplitude histograms obtained at several pipette potentials could be reasonably fitted with a single Gaussian corresponding to a single channel type with a slope conductance of 37 +/- 11 pS. The extrapolated equilibrium potential of the outward current was about 5 +/- 10 mV positive to the resting potential and both the channel open time constant and relative open time probability were sensitive to membrane potential, increasing markedly with depolarisation. The results presented in this paper show the presence of a cadmium-insensitive, voltage-dependent outward potassium channel in insect glial cells in vitro.
Keen
L
L
School of Biological and Molecular Sciences, Oxford Brookes University, Headington, Oxford, UK.
Amar
M
M
Beadle
D J
DJ
Bermudez
I
I
D000818:Animals; D002478:Cells, Cultured; D015640:Ion Channel Gating / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D009457:Neuroglia / Q000648:ultrastructure*; D010526:Periplaneta; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels