title: NMDA receptor activation contributes to a portion of the decreased mitochondrial membrane potential and elevated intracellular free calcium in strain-injured neurons.
abstract: In our previous studies, we have shown that in vitro biaxial strain (stretch) injury of neurons in neuronal plus glial cultures increases intracellular free calcium ([Ca(2+)](i)) and decreases mitochondrial membrane potential (deltapsi(m)). The goal of this study was to determine whether strain injury, without the addition of exogenous agents, causes glutamate release, and whether NMDA receptor antagonists affect the post-strain injury rise in [Ca(2+)](i) and decrease in deltapsi(m). [Ca(2+)](i) and deltapsi(m) were measured using the fluorescent indicators fura-2 AM and rhodamine-1,2,3 (rh123). Strain injury of neuronal plus glial cultures caused an immediate 100-200 nM elevation in neuronal [Ca(2+)]i and a decline in neuronal deltapsi(m) by 15 min post-injury. Pretreatment with the NMDA receptor antagonist MK-801 (10 microM) attenuated the [Ca(2+)](i) elevation after mild, but not moderate and severe injury. MK-801 pretreatment reduced the decline in deltapsi(m) after mild and moderate, but not after severe injury. The NMDA receptor antagonist D-2-amino-5-phosphonopentanoic acid (APV; 100 microM) had effects similar to MK-801. Simultaneous measurement of [Ca(2+)](i) and deltapsi(m) demonstrated a significant correlation and a temporal relationship between [Ca(2+)](i) elevation and depression of deltapsi(m). We conclude that NMDA receptor stimulation contributes to some of the changes in [Ca(2+)](i) and deltapsi(m) after less severe strain injury. However, after more pronounced injury other mechanisms appear to be more involved.
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298-0613, USA.
authors.forename: Syed M
authors.initials: SM
authors.lastname: Ahmed
authors.forename: John T
authors.initials: JT
authors.lastname: Weber
authors.forename: Shi
authors.initials: S
authors.lastname: Liang
authors.forename: Karen A
authors.initials: KA
authors.lastname: Willoughby
authors.forename: Heather A
authors.initials: HA
authors.lastname: Sitterding
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Rzigalinski
authors.forename: Earl F
authors.initials: EF
authors.lastname: Ellis
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002478:Cells, Cultured; D018920:Coculture Techniques; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes; D007425:Intracellular Membranes / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D016194:Receptors, N-Methyl-D-Aspartate; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D002118:Calcium