Persistent AMPA receptor stimulation alters [Ca2+]i homeostasis in cultures of embryonic dopaminergic neurons.
The effect of the ionotropic glutamate receptor agonist, AMPA, on intracellular Ca2+ concentrations ([Ca2+]i) was studied in dopaminergic neurons present in primary cultures of ventral tegmental mesencephalon of 14 day rat embryos. Exposure of cells to 10 microM AMPA for 1 min increased [Ca2+]i by 2-3 fold in dopaminergic and other neurons and this response was obliterated within 5 min by superfusion with AMPA-free incubation buffer. In dopaminergic neurons, 1 min or 5 min exposure to 50 microM AMPA increased [Ca2+]i 3 to 5 times over control values. This rise in [Ca2+]i persisted even after a 20 min superfusion with AMPA-free media, whereas, [Ca2+]i in non-dopaminergic neurons was reversed to control values during this time. Preincubation (2 min) of cultured cells with NBQX or the L-type channel blocker, nifedipine, but not with MK-801 blunted the rise of [Ca2+]i in dopaminergic and other neurons. Pretreatment with 2 microM NBQX shifted the dose response curve for AMPA to the right without changing the basal [Ca2+]i. The presence of 10 microM dantrolene, a blocker of Ca2+ release from intracellular stores, did not alter the initial rise of [Ca2+]i elicited by 50 microM AMPA, but prevented the destabilization of Ca2+ homeostasis by facilitating the recovery to normal of basal [Ca2+]i. Exposure to 50 microM AMPA (5 min) caused an irreversible increase of [Ca2+]i in dopaminergic neurons and cell death was manifested by propidium iodide uptake 6-7 h after AMPA exposure.(ABSTRACT TRUNCATED AT 250 WORDS)
de Erausquin
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Fidia Georgetown Institute for the Neurosciences, Georgetown University, Washington, DC 20007.
Brooker
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Costa
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Hanbauer
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I
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004298:Dopamine / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects* / Q000196:embryology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000187:drug effects*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D011810:Quinoxalines; D018091:Receptors, AMPA; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D002118:Calcium; D004298:Dopamine