title: SK channel regulation of dendritic excitability and dendrodendritic inhibition in the olfactory bulb.
abstract: Small-conductance calcium-activated potassium channels (SK) regulate dendritic excitability in many neurons. In the olfactory bulb, regulation of backpropagating action potentials and dendrodendritic inhibition depend on the dendritic excitability of mitral cells. We report here that SK channel currents are present in mitral cells but are not detectable in granule cells in the olfactory bulb. In brain slices from PND 14-21 mice, long step depolarizations (100 ms) in the mitral cell soma evoked a cadmium- and apamin-sensitive outward SK current lasting several hundred milliseconds. Block of the SK current unmasked an inward N-methyl-D-aspartate (NMDA) autoreceptor current due to glutamate released from mitral cell dendrites. In low extracellular Mg(2+) (100 microM), brief step depolarizations (2 ms) evoked an apamin-sensitive current that was reduced by D,L-2-amino-5-phosphonopentanoic acid. In current- clamp, block of SK channels increased action potential firing in mitral cells as well as dendrodendritic inhibition. Our results indicate that SK channels can be activated either by calcium channels or NMDA channels in mitral cell dendrites, providing a mechanism for local control of dendritic excitability.
authors.affiliation: Vollum Institute, Oregon Health and Science University, Portland, 97239, USA.
authors.forename: Brady J
authors.initials: BJ
authors.lastname: Maher
authors.forename: Gary L
authors.initials: GL
authors.lastname: Westbrook
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D000831:Animals, Newborn; D001030:Apamin / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003712:Dendrites / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009830:Olfactory Bulb / Q000166:cytology*; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D011724:Pyridazines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D009435:Synaptic Transmission / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D011724:Pyridazines; D011810:Quinoxalines; D002104:Cadmium; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D001030:Apamin; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D015763:2-Amino-5-phosphonovalerate; C049853:gabazine; D008274:Magnesium; D002118:Calcium