Differential expression of TASK channels between horizontal interneurons and pyramidal cells of rat hippocampus.
Among the electrophysiological properties differentiating stratum oriens horizontal interneurons from pyramidal neurons of the CA1 hippocampal subfield are the more depolarized resting potential and the higher input resistance; additionally, these interneurons are also less sensitive to ischemic damage than pyramidal cells. A differential expression of pH-sensitive leakage potassium channels (TASK) could contribute to all of these differences. To test this hypothesis, we studied the expression and properties of TASK channels in the two cell types. Electrophysiological recordings from acute slices showed that barium- and bupivacaine-sensitive TASK currents were detectable in pyramidal cells but not in interneurons and that extracellular acidification caused a much stronger depolarization in pyramidal cells than in interneurons. This pyramidal cell depolarization was paralleled by an increase of the input resistance, suggesting the blockade of a background conductance. Single-cell reverse transcription-PCR experiments showed that the expression profile of TASK channels differ between the two cell types and suggested that these channels mediate an important share of the leakage current of pyramidal cells. We suggest that the different expression of TASK channels in these cell types contribute to their electrophysiological differences and may result in cell-specific sensitivity to extracellular acidification in conditions such as epilepsy and ischemia.
Taverna
Stefano
S
Department of Physiology, Feinberg School of Medicine, Institute for Neuroscience, Northwestern University, Chicago, Illinois 60611, USA.
Tkatch
Tatiana
T
Metz
Alexia E
AE
Martina
Marco
M
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001464:Barium / Q000494:pharmacology; D002045:Bupivacaine / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007395:Interneurons / Q000378:metabolism*; D007530:Isoflurane / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins; D018408:Patch-Clamp Techniques / Q000379:methods; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism*; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D000779:Anesthetics, Local; D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C420132:potassium channel subfamily K member 3; D001464:Barium; D007530:Isoflurane; D002045:Bupivacaine