title: Zn2+ influx is critical for some forms of spreading depression in brain slices.
abstract: Spreading depression (SD) is wave of profound depolarization that propagates throughout brain tissue and can contribute to the spread of injury after stroke or traumatic insults. The contribution of Ca(2+) influx to SD differs depending on the stimulus, and we show here that Zn(2+) can play a critical complementary role in murine hippocampal slices. In initial studies, we used the Na(+)/K(+) ATPase inhibitor ouabain and found conditions in which SD was always prevented by L-type Ca(2+) channel blockers; however, Ca(2+) influx was not responsible for L-type effects. Cytosolic Ca(2+) increases were not detectable in CA1 neurons before SD, and removal of extracellular Ca(2+) did not prevent ouabain-SD. In contrast, cytosolic Zn(2+) increases were observed in CA1 neurons before ouabain-SD, and L-type channel block prevented the intracellular Zn(2+) rises. A slow mitochondrial depolarization observed before ouabain-SD was abolished by L-type channel block, and Zn(2+) accumulation contributed substantially to initial mitochondrial depolarizations. Selective chelation of Zn(2+) with N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) abolished SD, implying that Zn(2+) entry can play a critical role in the generation of ouabain-SD. TPEN was most effective when synaptic activity was reduced by adenosine A(1) receptor activation, and a combination of Ca(2+) and Zn(2+) removal was required to prevent ouabain-SD when A(1) receptors were blocked. Similarly, Zn(2+) chelation could prevent SD triggered by oxygen/glucose deprivation but Zn(2+) accumulation did not contribute to SD triggered by localized high K(+) exposures. These results identify Zn(2+) as a new target for the block of spreading depolarizations after brain injury.
authors.affiliation: Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Dietz
authors.forename: John H
authors.initials: JH
authors.lastname: Weiss
authors.forename: Claude W
authors.initials: CW
authors.lastname: Shuttleworth
mesh_terms: D058916:Adenosine A1 Receptor Antagonists; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D013181:Cortical Spreading Depression / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology*; D000860:Hypoxia / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008815:Mice, Inbred Strains; D008928:Mitochondria / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000008:administration & dosage / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D015032:Zinc / Q000378:metabolism*
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D005029:Ethylenediamines; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; D011188:Potassium; D002118:Calcium