Whole-cell recording from honeybee olfactory receptor neurons: ionic currents, membrane excitability and odourant response in developing workerbee and drone.
Whole-cell recording techniques were used to characterize ionic membrane currents and odourant responses in honeybee olfactory receptor neurons (ORNs) in primary cell culture. ORNs of workerbee (female) and drone (male) were isolated at an early stage of development before sensory axons connect to their target in the antennal lobe. The results collectively indicate that honeybee ORNs have electrical properties similar, but not necessarily identical to, those currently envisaged for ORNs of other species. Under voltage clamp at least four ionic currents could be distinguished. Inward currents were made of a fast transient, tetrodotoxin-sensitive sodium current. In some ORNs a cadmium-sensitive calcium current was detected. ORNs showed heterogeneity in their outward currents: either outward currents were made of a delayed rectifier type potassium current, which was partially blocked by tetraethyl ammonium or quinidine, or were composed of a delayed rectifier type and a transient calcium-dependent potassium current, which was cadmium-sensitive and abolished by removal of external calcium. The proportion of each of the two outward currents, however, was different within the ORNs of the two sexes suggesting a gender-specific functional heterogeneity. ORNs showed heterogeneity in action potential firing properties: depolarizing current steps elicited either one action potential or, as in most of the cells, it led to repetitive spiking. Action potentials were tetrodotoxin-sensitive suggesting they are carried by sodium. Odourant stimulation with different mixtures and pure substances evoked depolarizing receptor potentials with superimposed action potentials when spike threshold was reached. In summary, honeybee ORNs are remarkably mature at early stages in their development.
Laurent
Stéphanie
S
Centre Européen des Sciences du Goût, CNRS, 15, rue Hugues Picardet, F-21000 Dijon, France.
Masson
Claudine
C
Jakob
Ingrid
I
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001516:Bees / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D048429:Cell Size / Q000502:physiology; D002478:Cells, Cultured; D004558:Electric Stimulation; D005260:Female; D017952:Ganglia, Invertebrate / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D008297:Male; D009833:Olfactory Pathways / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D010675:Pheromones / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism; D018035:Receptors, Odorant / Q000187:drug effects / Q000378:metabolism; D012727:Sex Characteristics; D012903:Smell / Q000502:physiology*
D007473:Ion Channels; D010675:Pheromones; D024681:Potassium Channels, Calcium-Activated; D018035:Receptors, Odorant