Zn2+ influx is critical for some forms of spreading depression in brain slices.
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.
Dietz
Robert M
RM
Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA.
Weiss
John H
JH
Shuttleworth
Claude W
CW
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*
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