title: Mechanisms underlying odorant-induced and spontaneous calcium signals in olfactory receptor neurons of spiny lobsters, Panulirus argus.
abstract: We determined if a newly developed antennule slice preparation allows studying chemosensory properties of spiny lobster olfactory receptor neurons under in situ conditions with Ca(2+) imaging. We show that chemical stimuli reach the dendrites of olfactory receptor neurons but not their somata, and that odorant-induced Ca(2+) signals in the somata are sufficiently stable over time to allow stimulation with a substantial number of odorants. Pharmacological manipulations served to elucidate the source of odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations in the somata of olfactory receptor neurons. Both Ca(2+) signals are primarily mediated by an influx of extracellular Ca(2+) through voltage-activated Ca(2+) channels that can be blocked by CoCl2 and the L-type Ca(2+) channel blocker verapamil. Intracellular Ca(2+) stores contribute little to odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations. The odorant-induced Ca(2+) transients as well as the spontaneous Ca(2+) oscillations depend on action potentials mediated by Na(+) channels that are largely TTX-insensitive but blocked by the local anesthetics tetracaine and lidocaine. Collectively, these results corroborate the conclusion that odorant-induced Ca(2+) transients and spontaneous Ca(2+) oscillations in the somata of olfactory receptor neurons closely reflect action potential activity associated with odorant-induced phasic-tonic responses and spontaneous bursting, respectively. Therefore, both types of Ca(2+) signals represent experimentally accessible proxies of spiking.
authors.affiliation: Neuroscience Institute and Department of Biology, Georgia State University, P.O. Box 5030, Atlanta, GA, 30302-5030, USA.
authors.forename: Tizeta
authors.initials: T
authors.lastname: Tadesse
authors.forename: Charles D
authors.initials: CD
authors.lastname: Derby
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmidt
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology*; D061848:Optical Imaging; D033521:Palinuridae / Q000502:physiology*; D012903:Smell / Q000187:drug effects / Q000502:physiology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D002118:Calcium