In vitro characterization of L-type calcium channels and their contribution to firing behavior in invertebrate respiratory neurons.
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.
Spafford
J David
JD
Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
Dunn
Tyler
T
Smit
August B
AB
Syed
Naweed I
NI
Zamponi
Gerald W
GW
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*
D020746:Calcium Channels, L-Type