Unique properties of R-type calcium currents in neocortical and neostriatal neurons.
Whole cell recordings from acutely dissociated neocortical pyramidal neurons and striatal medium spiny neurons exhibited a calcium-channel current resistant to known blockers of L-, N-, and P/Q-type Ca(2+) channels. These R-type currents were characterized as high-voltage-activated (HVA) by their rapid deactivation kinetics, half-activation and half-inactivation voltages, and sensitivity to depolarized holding potentials. In both cell types, the R-type current activated at potentials relatively negative to other HVA currents in the same cell type and inactivated rapidly compared with the other HVA currents. The main difference between cell types was that R-type currents in neocortical pyramidal neurons inactivated at more negative potentials than R-type currents in medium spiny neurons. Ni(2+) sensitivity was not diagnostic for R-type currents in either cell type. Single-cell RT-PCR revealed that both cell types expressed the alpha1E mRNA, consistent with this subunit being associated with the R-type current.
Foehring
R C
RC
Department of Anatomy and Neurobiology, University of Tennessee, Memphis, Tennessee 38163, USA. foehring@nb.utmem.edu
Mermelstein
P G
PG
Song
W J
WJ
Ulrich
S
S
Surmeier
D J
DJ
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020908:Calcium Channels, R-Type / Q000235:genetics* / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D019579:Neocortex / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D017072:Neostriatum / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000737:chemistry* / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020867:omega-Agatoxin IVA / Q000494:pharmacology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020908:Calcium Channels, R-Type; D020747:Calcium Channels, T-Type; D012333:RNA, Messenger; D020867:omega-Agatoxin IVA; D009532:Nickel; D020866:omega-Conotoxin GVIA; D009543:Nifedipine