title: In vitro characterization of L-type calcium channels and their contribution to firing behavior in invertebrate respiratory neurons.
abstract: L-type calcium channel activity has been associated with a number of cytoplasmic responses, including gene transcription and activation of calcium-dependent enzymes, yet their direct contribution to the electrical activities of neurons has remained largely unexplored. Here we report the cloning and functional characterization of a molluscan L-type calcium channel homologue, LCa(v)1, and investigate its role in coordinating neuronal firing patterns. The LCav1 channel exhibits many hallmarks of vertebrate L-type channels in that it is high-voltage activated, slowly inactivating, and dihydropyridine sensitive and displays calcium-dependent inactivation in recording solutions with standard EGTA concentrations. We show that despite comprising less than approximately 20% of the total whole cell current in identified Lymnaea respiratory network neurons, the L-type channels are essential for maintaining rhythmic action potential discharges without being involved in synaptic release. Our data therefore suggest an important role of L-type calcium channels in maintaining rhythmical pattern activity underlying breathing behavior in Lymnaea.
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: J David
authors.initials: JD
authors.lastname: Spafford
authors.forename: Tyler
authors.initials: T
authors.lastname: Dunn
authors.forename: August B
authors.initials: AB
authors.lastname: Smit
authors.forename: Naweed I
authors.initials: NI
authors.lastname: Syed
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000502:physiology*; D008195:Lymnaea / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*
chemical_list: D020746:Calcium Channels, L-Type