title: Spreading depolarization triggered by elevated potassium is weak or absent in the rodent lower brain.
abstract: We examined in live coronal slices from rat and mouse which brain regions generate potassium-triggered spreading depolarization (SDKt). This technique simulates cortical spreading depression, which underlies migraine aura in the intact brain. An SDKtepisode was evoked by increasing bath [K+]oand recorded as a propagating front of elevated light transmittance representing transient neuronal swelling in gray matter of neocortex, hippocampus, striatum, and thalamus. In contrast, SDKtwas not imaged in hypothalamic nuclei or brainstem with exception of those nuclei near the dorsal brainstem surface. In rat slices, single neurons were whole-cell current clamped during SDKt. "Higher" neurons depolarized to near zero millivolts indicating SDKtgeneration. In contrast, seven types of neurons in hypothalamus and brainstem only slowly depolarized without generating SDKt, supporting our imaging findings. Therefore, SDKtis not a default of CNS neurons but rather displays a region-specific susceptibility, similar to anoxic depolarization, which we have proposed is correlated with a region's vulnerability to traumatic brain injury. In the higher brain, SDKtmay be a vestigial spreading depolarization that originally evolved to shut down and vasoconstrict gray matter regions more exposed to impact and contusion.
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
authors.forename: R David
authors.initials: RD
authors.lastname: Andrew
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Hsieh
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
authors.forename: C Devin
authors.initials: CD
authors.lastname: Brisson
mesh_terms: D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology*; D001933:Brain Stem / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D013181:Cortical Spreading Depression / Q000187:drug effects* / Q000502:physiology; D003470:Culture Media; D007031:Hypothalamus / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D061848:Optical Imaging; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003470:Culture Media; D011189:Potassium Chloride
keywords: Brainstem; ischemia; migraine aura; spreading depolarization; traumatic brain injury