Voltage- and calcium-activated currents in cultured olfactory receptor neurons of male Mamestra brassicae (Lepidoptera).
Insect olfactory receptor neurons (ORNs) grown in primary cultures were studied using the patch-clamp technique in both conventional and amphotericin B perforated whole-cell configurations under voltage-clamp conditions. After 10-24 days in vitro, ORNs had a mean resting potential of -62 mV and an average input resistance of 3.2 GOmega. Five different voltage-dependent ionic currents were isolated: one Na(+), one Ca(2+) and three K(+) currents. The Na(+) current (35-300 pA) activated between -50 and -30 mV and was sensitive to 1 microM tetrodotoxin (TTX). The sustained Ca(2+) current activated between -30 and -20 mV, reached a maximum amplitude at 0 mV (-4.5 +/- 6.0 pA) that increased when Ba(2+) was added to the bath and was blocked by 1 mM Co(2+). Total outward currents were composed of three K(+) currents: a Ca(2+)-activated K(+) current activated between -40 and -30 mV and reached a maximum amplitude at +40 mV (605 +/- 351 pA); a delayed-rectifier K(+) current activated between -30 and -10 mV, had a mean amplitude of 111 +/- 67 pA at +60 mV and was inhibited by 20 mM tetraethylammonium (TEA); and, finally, more than half of ORNs exhibited an A-like current strongly dependent on the holding potential and inhibited by 5 mM 4-aminopyridine (4-AP). Pheromone stimulation evoked inward current as measured by single channel recordings.
INRA, Unité de Phytopharmacie et des Médiateurs Chimiques, Route de Saint Cyr, 78026 Versailles Cedex, France. plucas@versailles.inra.fr
Philippe
P
Lucas
Takeshi
T
Shimahara
D000200:Action Potentials / Q000502:physiology; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000493:pharmacokinetics; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology; D007915:Lepidoptera / Q000166:cytology / Q000502:physiology*; D008297:Male; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010675:Pheromones / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D013997:Time Factors
D015220:Calcium Channels; D007473:Ion Channels; D010675:Pheromones; D001464:Barium; D000666:Amphotericin B; D012964:Sodium; D011188:Potassium; D002118:Calcium