Isoflurane enhances spontaneous Ca(2+) oscillations in developing rat hippocampal neurons in vitro.
BACKGROUND
During the nervous system development, spontaneous synchronized Ca(2+) oscillations are thought to possess integrative properties because their amplitude and frequency can influence the patterning of neuronal connection, neuronal differentiation, axon outgrowth, and long-distance wiring. Accumulating studies have confirmed that some drugs such as volatile anesthetic isoflurane produced histopathologic changes in the central nervous system in juvenile animal models. Because the hippocampus plays an important role in learning and memory, the present work was designed to characterize the Ca(2+) oscillations regulated by volatile anesthetic isoflurane in primary cultures of developing hippocampal neurons (5-day-cultured).


METHODS
Primary cultures of rat hippocampal neurons (5-day-cultured) were loaded with the Ca(2+) indicator Fluo-4AM (4 microM) and were studied with a confocal laser microscope.


RESULTS
Approximately 22% of 5-day-cultured hippocampal neurons exhibited typical Ca(2+) oscillations. These oscillations were dose-dependently enhanced by isoflurane (EC50 0.5 MAC, minimum alveolar concentration) and this effect could be reverted by bicuculline (50 microM), a specific gamma-aminobutyric acid (GABA(A)) receptor antagonist.


CONCLUSIONS
Unlike its depressant effect on the Ca(2+) oscillations in adult neurons in previous researches, isoflurane dose-dependently enhanced calcium oscillations in developing hippocampal neurons by activating GABA(A) receptors, a major excitatory receptor in synergy with N-methyl-d-aspartate receptors at the early stages of development. It may be involved in the mechanism of an isoflurane-induced neurotoxic effect in the developing rodent brain.
Xiang
Q
Q
Department of Anesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Tan
L
L
Zhao
Y-L
YL
Wang
J-T
JT
Jin
X-G
XG
Luo
A-L
AL
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects / Q000196:embryology; D007530:Isoflurane / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects*; D009529:Nicardipine / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects
D018685:Anesthetics, Inhalation; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D011963:Receptors, GABA-A; D016291:Dizocilpine Maleate; D007530:Isoflurane; D009529:Nicardipine; D001640:Bicuculline