Differential hippocampal protection when blocking intracellular sodium and calcium entry during traumatic brain injury in rats.
This study investigated the contributions of the reverse mode of the sodium-calcium exchanger (NCX) and the type 1 sodium-proton antiporter (NHE-1) to acute astrocyte and neuronal pathology in the hippocampus following fluid percussion traumatic brain injury (TBI) in the rat. KB-R7943, EIPA, or amiloride, which respectively inhibit NCX, NHE-1, or NCX, NHE-1, and ASIC1a (acid-sensing ion channel type 1a), was infused intraventricularly over a 60-min period immediately prior to TBI. Astrocytes were immunostained for glial fibrillary acidic protein (GFAP), and degenerating neurons were identified by Fluoro-Jade staining at 24 h after injury. Stereological analysis of the CA2/3 sub-regions of the hippocampus demonstrated that higher doses of KB-R7943 (2 and 20 nmoles) significantly reduced astrocyte GFAP immunoreactivity compared to vehicle-treated animals. EIPA (2-200 nmoles) did not alter astrocyte GFAP immunoreactivity. Amiloride (100 nmoles) significantly attenuated the TBI-induced acute reduction in astrocyte GFAP immunoreactivity. Of the three compounds examined, only amiloride (100 nmoles) reduced hippocampal neuronal degeneration assessed with Fluoro-Jade. The results provide additional evidence of acute astrocyte pathology in the hippocampus following TBI, while suggesting that activation of NHE-1 and the reverse mode of NCX contribute to both astrocyte and neuronal pathology following experimental TBI.
Department of Neurological Surgery, University of California at Davis, Davis, California 95616-8797, USA.
Xueren
X
Zhao
Fredric A
FA
Gorin
Robert F
RF
Berman
Bruce G
BG
Lyeth
D062565:Acid Sensing Ion Channels; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D001930:Brain Injuries / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis / Q000378:metabolism; D005911:Gliosis / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D007276:Injections, Intraventricular; D008297:Male; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000187:drug effects / Q000378:metabolism
D062565:Acid Sensing Ion Channels; D015415:Biomarkers; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1