title: Membrane properties of microglial cells isolated from the leech central nervous system.
abstract: Membrane potentials and channel properties of microglial cells isolated from the leech central nervous system and maintained in culture on different substrates were investigated by using the patch-clamp technique. As expected, microglia on concanavalin A (con-A) were round and stationary, whereas those on extract of extracellular matrix (ECM) were spindle shaped and mobile. The mean membrane capacitance was 9 +/- 1 pF (s.e., n = 46), and the input resistance ranged from 0.135 G omega to 21 G omega with a mean of 4.2 +/- 1.6 G omega (n = 19). On-cell patches exhibited no single-channel activity. Voltage-dependent Na+, K+ and Ca2+ currents typical of neurons were absent. Currents evoked in response to voltage ramps from -100 mV to +100 mV or to steps of 4 s duration reversed in sign at or near 0 mV and exhibited single-channel activity of increasing amplitude for incrementally larger positive and negative voltage steps. No differences between the membrane properties of microglial cells on con-A and on ECM were evident. Currents were increased in fluid in which Na+ was substituted with K+, and were decreased when Na+ was substituted with N-methyl-D-glucamine. Varying external [Cl-] was without effect, as was addition to the fluid of 100 microM anthracene-9-carboxylate, a Cl- channel blocker. Together these characteristics indicated a cation channel. Bath application of 100 microM serotonin reversibly increased both inward and outward currents as well as single-channel activity. It is concluded that cultured microglial cells isolated from the adult leech have high membrane resistance and cation channel activity influenced by serotonin.
authors.affiliation: Department of Pharmacology, University of Basel, Switzerland.
authors.forename: R R
authors.initials: RR
authors.lastname: Stewart
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects; D017952:Ganglia, Invertebrate / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D007865:Leeches; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D009424:Nervous System Physiological Phenomena; D012701:Serotonin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D007473:Ion Channels; D012701:Serotonin