title: Reduced Ca2+ spark activity after subarachnoid hemorrhage disables BK channel control of cerebral artery tone.
abstract: Intracellular Ca(2+) release events ('Ca(2+) sparks') and transient activation of large-conductance Ca(2+)-activated potassium (BK) channels represent an important vasodilator pathway in the cerebral vasculature. Considering the frequent occurrence of cerebral artery constriction after subarachnoid hemorrhage (SAH), our objective was to determine whether Ca(2+) spark and BK channel activity were reduced in cerebral artery myocytes from SAH model rabbits. Using laser scanning confocal microscopy, we observed ∼50% reduction in Ca(2+) spark activity, reflecting a decrease in the number of functional Ca(2+) spark discharge sites. Patch-clamp electrophysiology showed a similar reduction in Ca(2+) spark-induced transient BK currents, without change in BK channel density or single-channel properties. Consistent with a reduction in active Ca(2+) spark sites, quantitative real-time PCR and western blotting revealed decreased expression of ryanodine receptor type 2 (RyR-2) and increased expression of the RyR-2-stabilizing protein, FKBP12.6, in the cerebral arteries from SAH animals. Furthermore, inhibitors of Ca(2+) sparks (ryanodine) or BK channels (paxilline) constricted arteries from control, but not from SAH animals. This study shows that SAH-induced decreased subcellular Ca(2+) signaling events disable BK channel activity, leading to cerebral artery constriction. This phenomenon may contribute to decreased cerebral blood flow and poor outcome after aneurysmal SAH.
authors.affiliation: Department of Pharmacology, University of Vermont College of Medicine, Burlington, Vermont, USA.
authors.forename: Masayo
authors.initials: M
authors.lastname: Koide
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Nystoriak
authors.forename: Gayathri
authors.initials: G
authors.lastname: Krishnamoorthy
authors.forename: Kevin P
authors.initials: KP
authors.lastname: O'Connor
authors.forename: Adrian D
authors.initials: AD
authors.lastname: Bonev
authors.forename: Mark T
authors.initials: MT
authors.lastname: Nelson
authors.forename: George C
authors.initials: GC
authors.lastname: Wellman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D020013:Calcium Signaling / Q000502:physiology*; D002536:Cerebral Arteries / Q000473:pathology / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D055724:Electrophysiological Phenomena; D006706:Homeostasis / Q000502:physiology; D008297:Male; D009129:Muscle Tonus / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D009422:Nervous System Diseases / Q000209:etiology; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D011312:Pressure; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019837:Ryanodine Receptor Calcium Release Channel / Q000096:biosynthesis / Q000235:genetics; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D022021:Tacrolimus Binding Proteins / Q000235:genetics / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D024681:Potassium Channels, Calcium-Activated; D019837:Ryanodine Receptor Calcium Release Channel; D012313:RNA; D022021:Tacrolimus Binding Proteins; C403484:tacrolimus binding protein 1B