title: Differential expression of voltage-sensitive K+ and Ca2+ currents in neurons of the honeybee olfactory pathway.
abstract: In order to understand the neuronal processes underlying olfactory learning, biophysical properties such as ion channel activity need to be analysed within neurons of the olfactory pathway. This study analyses voltage-sensitive ionic currents of cultured antennal lobe projection neurons and mushroom body Kenyon cells in the brain of the honeybee Apis mellifera. Rhodamine-labelled neurons were identified in vitro prior to recording, and whole-cell K(+) and Ca(2+) currents were measured. All neurons expressed transient and sustained outward K(+) currents, but Kenyon cells expressed higher relative amounts of transient A-type K(+) (I(K,A)) currents than sustained delayed rectifier K(+) current (I(K,V)). The current density of the I(K,V) was significantly higher in projection neurons than in Kenyon cells. The voltage-dependency of K(+) currents at positive membrane potentials was linear in Kenyon cells, but N-shaped in projection neurons. Blocking of voltage-sensitive Ca(2+) currents transformed the N-shaped voltage-dependency into a linear one, indicating activation of calcium-dependent K(+) currents (I(K,Ca)). The densities of currents through voltage-sensitive Ca(2+) channels did not differ between the two neuron classes and the voltage-dependency of current activation was similar. Projection neurons thus express higher calcium-dependent K(+) currents. These analyses revealed that the various neurons of the honeybee olfactory pathway in vitro have different current phenotypes, which may reflect functional differences between the neuron types in vivo.
authors.affiliation: Institut für Biologie, Neurobiologie, Freie Universität Berlin, Königin-Luise-Strasse 28/30, D-14195 Berlin, Germany. gruenewa@neurobiologie.fu-berlin.de
authors.forename: Bernd
authors.initials: B
authors.lastname: Grünewald
mesh_terms: D000818:Animals; D001516:Bees / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D066298:In Vitro Techniques; D017136:Ion Transport; D008564:Membrane Potentials; D009833:Olfactory Pathways / Q000166:cytology / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D011188:Potassium; D002118:Calcium