Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons.
The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively most important voltage dependent calcium channel in all parts of the neuron. After treatment with thapsigargin the increase in cytosolic calcium was halved, indicating that calcium release from thapsigargin sensitive intracellular calcium stores is an important component of the potassium induced rise in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears to predominate in all compartments.
Timmermann
D B
DB
Neuroscience Research Center, Department of Pharmacology, The Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100, Copenhagen, Denmark.
Lund
T M
TM
Belhage
B
B
Schousboe
A
A
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism*; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005333:Fetus; D016257:Fura-2 / Q000493:pharmacokinetics; D018755:GABA Agonists / Q000494:pharmacology; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D019579:Neocortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009557:Nipecotic Acids / Q000494:pharmacology; D027361:Organic Anion Transporters; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology; D000078308:Tiagabine; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002352:Carrier Proteins; D002614:Chelating Agents; D018755:GABA Agonists; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009557:Nipecotic Acids; D027361:Organic Anion Transporters; D015222:Sodium Channels; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D011188:Potassium; D002118:Calcium; D016257:Fura-2; D000078308:Tiagabine