Skip Navigation LinksHome > September 2014 - Volume 121 - Issue 3 > General Anesthetic Isoflurane Modulates Inositol 1,4,5-Trisp...
Anesthesiology:
doi: 10.1097/ALN.0000000000000316
Perioperative Medicine: Basic Science

General Anesthetic Isoflurane Modulates Inositol 1,4,5-Trisphosphate Receptor Calcium Channel Opening

Joseph, J. Donald Ph.D.; Peng, Yi M.D.; Mak, Don-On Daniel Ph.D.; Cheung, King-Ho Ph.D.; Vais, Horia Ph.D.; Foskett, J. Kevin Ph.D.; Wei, Huafeng M.D., Ph.D.

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Abstract

Background: Pharmacological evidence suggests that inhalational general anesthetics induce neurodegeneration in vitro and in vivo through overactivation of inositol trisphosphate receptor (InsP3R) Ca2+-release channels, but it is not clear whether these effects are due to direct modulation of channel activity by the anesthetics.
Methods: Using single-channel patch clamp electrophysiology, the authors examined the gating of rat recombinant type 3 InsP3R (InsP3R-3) Ca2+-release channels in isolated nuclei (N = 3 to 15) from chicken lymphocytes modulated by isoflurane at clinically relevant concentrations in the absence and presence of physiological levels of the agonist inositol 1,4,5-trisphosphate (InsP3). The authors also examined the effects of isoflurane on InsP3R-mediated Ca2+ release from the endoplasmic reticulum and changes in intracellular Ca2+ concentration ([Ca2+]i).
Results: Clinically relevant concentrations (approximately 1 minimal alveolar concentration) of the commonly used general anesthetic, isoflurane, activated InsP3R-3 channels with open probability similar to channels activated by 1 µM InsP3 (Po ≈ 0.2). This isoflurane modulation of InsP3R-3 Po depended biphasically on [Ca2+]i. Combination of isoflurane with subsaturating levels of InsP3 in patch pipettes resulted in at least two-fold augmentations of InsP3R-3 channel Po compared with InsP3 alone. These effects were not noted in the presence of saturating [InsP3]. Application of isoflurane to DT40 cells resulted in a 30% amplification of InsP3R-mediated [Ca2+]i oscillations, whereas InsP3-induced increase in [Ca2+]i and cleaved caspase-3 activity were enhanced by approximately 2.5-fold.
Conclusion: These results suggest that the InsP3R may be a direct molecular target of isoflurane and plays a role in the mechanisms of anesthetic-mediated pharmacological or neurotoxic effects.

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