J Anesth Perioper Med. 2017;4(2):45-59. https://doi.org/10.24015/ebcmed.japm.2017.0016
From Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville, USA.
Correspondence to Dr. Carl Lynch III at CL7Y@virginia.edu.
EBCMED ID: ebcmed.japm.2017.0016 DOI: 10.24015/ebcmed.japm.2017.0016
Volatile anesthetics (VAs) are known to have actions on a variety of ligand-and voltage gated ion channels, and thereby inhibit neuronal function. VA effects mediated by actions on voltage-gated Ca channels (VGCCs) were determined by studying their effects on the depolarization-induced rise in intracellular Ca2+ transients and the consequent glutamate release in cultured neonatal rat cerebellar granule neurons.
Using a glutamate dehydrogenase-coupled assay for glutamate release, and fura-2 to measure intracellular [Ca2+] ([Ca2+]i), neurons at 37℃ were depolarized by a rapid increase in [K+]o from 5 to 55 mM. Actions of halothane, isoflurane, enflurane, and sevoflurane were compared with effects of altered [Mg2+]o, and by specific blockade of L- , P/Q- and/or N-type VGCC by nicardipine, ω-agatoxin IVA, and ω-conotoxin-GVIA, respectively. Whole-cell patch-clamp studies in these same neurons of VGCC Ba2+ currents were also performed at 22℃.
Clinical VA concentrations dose-dependently depressed both peak [Ca2+]i and glutamate release by 35-70%. With N- and/or L-type VGCC blockade, VAs caused a further marked decrease in [Ca2+]i transients. VAs depressed whole cell patch-clamped Ba2+ currents in these granule cell neurons by 35-40%.
VAs depress Ca2+ entry by inhibiting a variety of VGCCs, and thereby reduce neuronal glutamate release. This action may contribute to the mechanism of anesthesia as well as provide protection during ischemic insults that cause neuronal injury.
Declaration of Interests
The authors declared no other competing interests.
This study was supported by National Institutes of Health (NIH) Grant R01GM31144.
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