Domoic acid neurotoxicity in cultured cerebellar granule neurons is controlled preferentially by the NMDA receptor Ca(2+) influx pathway.
We have monitored real-time alterations in [Ca(2+)](i) in fluo-3-loaded cerebellar granule neurons exposed to domoate, and ascertained the influence of pharmacological blockers of various Ca(2+) entry pathways on intracellular Ca(2+) accumulation, excitatory amino acid (EAA) release and neuronal death. Domoate produced a rapid and concentration-dependent increase in [Ca(2+)](i), the magnitude of which correlated closely with the severity of neuron loss. The increase in [Ca(2+)](i) was derived from activation of NMDA receptors, L-type voltage-sensitive calcium channels (VSCC) and the reversed mode of operation of the Na(+)/Ca(2+) exchanger. When the level of neuroprotection conferred by pharmacological manipulation of these calcium entry pathways was regressed with the corresponding reductions in [Ca(2+)](i) load, it was observed that neuronal vulnerability is controlled preferentially by NMDA receptors. This observation is consistent with our previous study of brevetoxin-induced autocrine excitotoxicity and with the source specificity hypothesis of others [J. Neurochem. 71 (1998) 2349], which suggests that elevation of [Ca(2+)](i) in the vicinity of the NMDA receptor ion channel activates processes leading to neuronal death.
Berman
Frederick W
FW
Department of Physiology and Pharmacology, Rm 2223, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602-7389, USA.
LePage
Keith T
KT
Murray
Thomas F
TF
D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000378:metabolism; D005456:Fluorescent Dyes; D007608:Kainic Acid / Q000031:analogs & derivatives* / Q000633:toxicity*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D009467:Neuromuscular Depolarizing Agents / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D014966:Xanthenes
D000814:Aniline Compounds; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D005456:Fluorescent Dyes; D009467:Neuromuscular Depolarizing Agents; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D019831:Sodium-Calcium Exchanger; D014966:Xanthenes; C059715:Fluo-3; D007770:L-Lactate Dehydrogenase; C012301:domoic acid; D007608:Kainic Acid