title: Sustained Ca2+-induced Ca2+-release underlies the post-glutamate lethal Ca2+ plateau in older cultured hippocampal neurons.
abstract: Several studies have shown that a prolonged Ca(2+) elevation follows a glutamate-mediated excitotoxic insult in cultured neurons, and may be associated with impending cell death. Recently, we showed that the prolonged Ca(2+) elevation that emerges as neurons age in culture is specifically linked to an age-related increase in excitotoxic vulnerability. However, the multiple sources of Ca(2+) that contribute to Ca(2+) elevation during and after glutamate exposure are not well understood. Here, we examined the Ca(2+) sources of the age-related prolonged Ca(2+) elevation in cultured hippocampal neurons. Studies with caffeine showed that the ryanodine receptor-dependent releasable pool of Ca(2+) from intracellular stores was similar in older and younger neurons. Thapsigargin, which inhibits intracellular store refilling, did not mimic the age-related prolonged Ca(2+) elevation and, in fact, partially reduced it. Ryanodine, which blocks Ca(2+)-induced Ca(2+)-release (CICR) from stores, completely blocked the age-related prolonged Ca(2+) elevation following glutamate exposure but did not alter maximal Ca(2+) elevation during the glutamate exposure. Thus, we conclude that sustained CICR plays a selective and key role in generating the lethal, age-related, prolonged Ca(2+) elevation, and is the likely mechanism underlying age-related, enhanced vulnerability to excitotoxicity in neurons.
authors.affiliation: University of Kentucky Medical Center, Department of Molecular and Biomedical Pharmacology, MS-320, 800 Rose Street, Lexington, KY 40536, USA.
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Clodfelter
authors.forename: Nada M
authors.initials: NM
authors.lastname: Porter
authors.forename: Philip W
authors.initials: PW
authors.lastname: Landfield
authors.forename: Olivier
authors.initials: O
authors.lastname: Thibault
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D016922:Cellular Senescence; D018698:Glutamic Acid / Q000633:toxicity*; D006624:Hippocampus / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D012433:Ryanodine; D002110:Caffeine; D018698:Glutamic Acid; D019284:Thapsigargin; D002118:Calcium