title: Iberiotoxin-sensitive large conductance Ca2+ -dependent K+ (BK) channels regulate the spike configuration in the burst firing of cerebellar Purkinje neurons.
abstract: Cerebellar Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex. Mature PCs discharge either tonically Na+ spikes or bursts of Na+ spikes ending to a Ca2+ spike. These cells express inactivating and non-inactivating large conductance Ca2+ -dependent K+ (BK) channels in their soma and dendrites. Somatic intracellular recording of acutely prepared brain slices was performed to examine the role of BK channels-mediated current in the tonic and burst firing of PCs. Continuous injection of a negative DC current was used to both suppress the spontaneous activity and stabilize the resting membrane potential around -70 mV. Then, the short depolarizing current injection was used to evoke spike discharge. For establishing of the burst firing, 4-aminopyridine (4-AP) was bath applied to the bath solution. Blockade of BK channels with iberiotoxin (IbTx); a specific blocker of BK channels, did not affect the Na+ spike configuration in the tonic firing but caused a remarkable change in the shape of Na+ and Ca2+ spikes in 4-AP-induced burst. Our results showed that during the burst firing, strong activation of IbTx-sensitive BK channels enhances the amplitude of fast afterhyperpolarization while decreases the duration of both Na+ and Ca2+ spikes. The current from these channels contributes to both the repolarizing of Na+ spike in the burst and setting of the amplitude of post-pulse AHP that occurs immediately after a depolarizing pulse. These data reveal an important role of IbTx-sensitive BK current in regulating of the spike configuration during the burst firing of PCs.
authors.affiliation: Department of Physiology and Medical Physics, Faculty of Medicine, Qazvin University of Medical Sciences, Qazvin, Iran. hhaghdoost@yahoo.com
authors.forename: Hashem
authors.initials: H
authors.lastname: Haghdoost-Yazdi
authors.forename: Mahyar
authors.initials: M
authors.lastname: Janahmadi
authors.forename: Gila
authors.initials: G
authors.lastname: Behzadi
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002531:Cerebellum / Q000166:cytology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D008297:Male; D018408:Patch-Clamp Techniques / Q000379:methods; D010455:Peptides / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D026902:Potassium Channel Blockers; D026941:Sodium Channel Blockers; D001030:Apamin; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C064719:iberiotoxin; D015761:4-Aminopyridine