title: Acute restraint stress enhances calcium mobilization and glutamate exocytosis in cerebrocortical synaptosomes from mice.
abstract: Acute stress is known to enhance the memory of events that are potentially threatening to the organisms. Glutamate, the most abundant excitatory neurotransmitter in the mammalian central nervous system, plays a critical role in learning and memory formation and calcium (Ca(2+)) plays an essential role in transmitter release from nerve terminals (synaptosomes). In the present study, we investigated the effects of acute restraint stress on cytosolic free Ca(2+) concentration ([Ca(2+)](i)) and glutamate release in cerebrocortical synaptosomes from mice. Acute restraint stress caused a significant increase in resting [Ca(2+)](i) and significantly enhanced the ability of the depolarizing agents K(+) and 4-aminopyridine (4-AP) to increase [Ca(2+)](i). It also brought about a significant increase in spontaneous (unstimulated) glutamate release and significantly enhanced K(+)- and 4-AP-induced Ca(2+)-dependent glutamate release. The pretreatment of synaptosomes with a combination of omega-agatoxin IVA (a P-type Ca(2+) channel blocker) and omega-conotoxin GVIA (an N-type Ca(2+) channel blocker) completely suppressed the enhancements of [Ca(2+)](i) and Ca(2+)-dependent glutamate release in acute restraint-stressed mice. These results indicate that acute restraint stress enhances K(+)- or 4-AP-induced glutamate release by increasing [Ca(2+)](i) via stimulation of Ca(2+) entry through P- and N-type Ca(2+) channels.
authors.affiliation: Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, 080-8555, Japan. es@obihiro.ac.jp
authors.forename: Eiki
authors.initials: E
authors.lastname: Satoh
authors.forename: Shusuke
authors.initials: S
authors.lastname: Shimeki
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D005089:Exocytosis / Q000187:drug effects; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D051379:Mice; D011188:Potassium / Q000494:pharmacology; D012149:Restraint, Physical / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology*; D013574:Synaptosomes / Q000378:metabolism*; D020867:omega-Agatoxin IVA / Q000494:pharmacology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020867:omega-Agatoxin IVA; D018698:Glutamic Acid; D020866:omega-Conotoxin GVIA; D015761:4-Aminopyridine; D011188:Potassium; D002118:Calcium; D003345:Corticosterone