title: Firing and intrinsic properties of antennal lobe neurons in the Noctuid moth Agrotis ipsilon.
abstract: The antennal lobe (AL) of the Noctuid moth Agrotis ipsilon has emerged as an excellent model for studying olfactory processing and its plasticity in the central nervous system. Odor-evoked responses of AL neurons and input-to-output transformations involved in pheromone processing are well characterized in this species. However, the intrinsic electrical properties responsible of the firing of AL neurons are poorly known. To this end, patch-clamp recordings in current- and voltage-clamp mode from neurons located in the two main clusters of cell bodies in the ALs were combined with intracellular staining on A. ipsilon males. Staining indicated that the lateral cluster (LC) is composed of 85% of local neurons (LNs) and 15% of projection neurons (PNs). The medial cluster (MC) contains only PNs. Action potentials were readily recorded from the soma in LNs and PNs located in the LC but not from PNs in the MC where recordings showed small or no action potentials. In the LC, the spontaneous activity of about 20% of the LNs presented irregular bursts while being more regular in PNs. We also identified a small population of LNs lacking voltage-gated Na(+) currents and generating spikelets. We focused on the firing properties of LNs since in about 60% of LNs, but not in PNs, action potentials were followed by depolarizing afterpotentials (DAPs). These DAPs could generate a second action potential, so that the activity was composed of action potential doublets. DAPs depended on voltage, Ca(2+)-channels and possibly on Ca(2+)-activated non-specific cationic channels. During steady state current injection, DAPs occurred after each action potential and did not require high-frequency firing. The amplitude of DAPs increased when the interspike interval was small, typically within bursts, likely arising from a Ca(2+) build up. DAPs were more often found in bursting than in non-bursting LNs but do not support bursting activity. DAPs and spike doublets also occurred during odor-evoked activity suggesting that they can mediate olfactory integration in the AL.
authors.affiliation: UMR 1392 Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), INRA, Route de Saint-Cyr, F-78026 Versailles cedex, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Lavialle-Defaix
authors.affiliation: UMR 1392 Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), INRA, Route de Saint-Cyr, F-78026 Versailles cedex, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Jacob
authors.affiliation: UMR 1392 Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), INRA, Route de Saint-Cyr, F-78026 Versailles cedex, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Monsempès
authors.affiliation: Neuroéthologie-RCIM, INRA-Université d'Angers, UPRES EA 2647 USC INRA 1330, 42 rue Georges Morel, 49071 Beaucouzé, France.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Anton
authors.affiliation: UMR 1392 Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), INRA, Route de Saint-Cyr, F-78026 Versailles cedex, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Rospars
authors.affiliation: UMR7503, Laboratoire Lorrain de Recherche en Informatique et ses Applications (LORIA), Centre National de la Recherche Scientifique (CNRS), Vandœuvre-lès-Nancy, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Martinez
authors.affiliation: UMR 1392 Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), INRA, Route de Saint-Cyr, F-78026 Versailles cedex, France. Electronic address: philippe.lucas@versailles.inra.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Lucas
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D057506:Arthropod Antennae / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D008959:Models, Neurological; D009036:Moths / Q000502:physiology*; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D012903:Smell / Q000502:physiology*
keywords: Antennal lobe; Depolarizing afterpotential; Firing; Local interneuron; Olfaction