The role of voltage-gated calcium channels in neurotransmitter phenotype specification: Coexpression and functional analysis in Xenopus laevis.
Calcium activity has been implicated in many neurodevelopmental events, including the specification of neurotransmitter phenotypes. Higher levels of calcium activity lead to an increased number of inhibitory neural phenotypes, whereas lower levels of calcium activity lead to excitatory neural phenotypes. Voltage-gated calcium channels (VGCCs) allow for rapid calcium entry and are expressed during early neural stages, making them likely regulators of activity-dependent neurotransmitter phenotype specification. To test this hypothesis, multiplex fluorescent in situ hybridization was used to characterize the coexpression of eight VGCC α1 subunits with the excitatory and inhibitory neural markers xVGlut1 and xVIAAT in Xenopus laevis embryos. VGCC coexpression was higher with xVGlut1 than xVIAAT, especially in the hindbrain, spinal cord, and cranial nerves. Calcium activity was also analyzed on a single-cell level, and spike frequency was correlated with the expression of VGCC α1 subunits in cell culture. Cells expressing Cav 2.1 and Cav 2.2 displayed increased calcium spiking compared with cells not expressing this marker. The VGCC antagonist diltiazem and agonist (-)BayK 8644 were used to manipulate calcium activity. Diltiazem exposure increased the number of glutamatergic cells and decreased the number of γ-aminobutyric acid (GABA)ergic cells, whereas (-)BayK 8644 exposure decreased the number of glutamatergic cells without having an effect on the number of GABAergic cells. Given that the expression and functional manipulation of VGCCs are correlated with neurotransmitter phenotype in some, but not all, experiments, VGCCs likely act in combination with a variety of other signaling factors to determine neuronal phenotype specification.
Department of Biology, College of William and Mary, Williamsburg, Virginia, 23185.
Brittany B
BB
Lewis
Lauren E
LE
Miller
Wendy A
WA
Herbst
Margaret S
MS
Saha
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001921:Brain / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000378:metabolism; D002478:Cells, Cultured; D003391:Cranial Nerves / Q000502:physiology; D059330:GABAergic Neurons / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D012160:Retina / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
C000595059:CACNA1A protein, Xenopus; C527798:CACNA1B protein, Xenopus; D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D018377:Neurotransmitter Agents; C493467:SLC17A7 protein, Xenopus; C529166:VIAAT protein, Xenopus; D050598:Vesicular Glutamate Transport Protein 1; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; D029867:Xenopus Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002118:Calcium
GABA; calcium activity; development; embryo; glutamate