Summary: A new study identifies the type 1 ryanodine receptor (RyR1) as a direct molecular target of inhalational anesthetics and clarifies a critical step in how these drugs induce general anesthesia. The researchers show that isoflurane and related volatile anesthetics activate RyR1, prompting calcium release from the endoplasmic reticulum (ER) and contributing to anesthetic and sedative effects in mice.
Using biochemical assays, targeted mutagenesis, and genetically engineered mice, the team linked RyR1 activation to behavioral loss of consciousness under isoflurane. Mice carrying an RyR1 mutation that prevents isoflurane activation displayed reduced sensitivity to anesthetic exposure. Complementary in silico screening also identified novel small molecules that bind the same RyR1 site and produce sedative-like effects, highlighting potential therapeutic avenues for safer anesthetics and treatments for anesthesia-related complications.
Key Facts:
- RyR1 Role Confirmed: The type 1 ryanodine receptor, a major ER calcium-release channel, is directly activated by inhalational anesthetics such as isoflurane.
- Genetic Evidence: Knock-in mice engineered with an RyR1 mutation that removes the response to isoflurane showed reduced anesthetic sensitivity, supporting RyR1’s causal role.
- Therapeutic Potential: Novel compounds targeting the proposed isoflurane binding pocket on RyR1 produced sedation in mice, suggesting new directions for drug development.
Source: Japan Science and Technology Agency
Inhalational anesthetics have been used clinically since the 1840s, yet the complete molecular basis for their effects has remained incompletely understood. Prior research implicated multiple neural ion channels—such as GABAA receptors and two-pore domain potassium (K2P) channels—in mediating anesthetic actions, and clinical observations have long hinted that other targets may contribute.
Clinically, rare RyR1 mutations increase the risk of malignant hyperthermia, a life-threatening hypermetabolic reaction that can be triggered by volatile anesthetics. Despite that association, direct molecular evidence that inhalational anesthetics act on RyR1 had been lacking.
The research led by Professor Hiroki Ueda at The University of Tokyo demonstrates that isoflurane and similar inhalational agents directly activate wild-type RyR1, causing calcium efflux from the endoplasmic reticulum. Systematic mutagenesis identified specific amino acid residues required for isoflurane sensitivity and allowed the team to estimate a likely anesthetic binding pocket on RyR1.
To establish the in vivo relevance of this interaction, investigators generated knock-in mice carrying an RyR1 variant that is insensitive to isoflurane. These mutant mice showed a measurable resistance to loss of righting reflex (LORR) when exposed to isoflurane, indicating a partial reduction in anesthetic effect. Complementary experiments showed RyR1 contributes to neuronal responses to isoflurane, supporting a physiological link between channel activation and behavioral sedation.
In parallel, the team performed in silico compound screening against the proposed binding site and identified new RyR1-targeting molecules. When administered to mice, several of these compounds produced sedative-like effects, mirroring the behavioral outcomes associated with isoflurane activation of RyR1. These findings suggest that modulation of RyR1 can alter consciousness and sedation, and that the receptor is a viable target for developing novel anesthetic agents or adjuncts.
Overall, this work adds a significant piece to the puzzle of how inhalational anesthetics work at the molecular level. It provides both mechanistic insight—demonstrating direct activation of an ER calcium-release channel by volatile anesthetics—and translational leads for therapeutics that could improve anesthetic safety or address adverse reactions such as malignant hyperthermia.
The study was published online in PLOS Biology on June 3, 2025 (EDT) and was performed under the Ueda Biological Timing Project, part of JST’s Exploratory Research for Advanced Technology (ERATO). That program uses systems biology approaches, including the sleep–wake rhythm model, to investigate biological timing from molecules to human behavior.
Notes:
(*1) Malignant hyperthermia: A genetically predisposed, potentially fatal increase in body temperature and metabolic activity triggered by certain anesthetics. RyR1 mutations are a common risk factor. Dantrolene, a RyR inhibitor, is an established treatment.
(*2) Endoplasmic reticulum: A membrane-bound cellular organelle that stores intracellular calcium. Controlled release from the ER helps regulate intracellular calcium concentrations and cell signaling.
(*3) Knock-in mouse: A genetically modified mouse in which specific sequence changes are introduced into the genome. In this study, the knock-in model carries a modified RyR1 gene that abolishes responsiveness to isoflurane.
About this neurology research news
Author: Satomi Kobayashi
Source: Japan Science and Technology Agency
Contact: Satomi Kobayashi – Japan Science and Technology Agency
Image: Image credit: Neuroscience News
Original Research: Open access.
“Isoflurane activates the type 1 ryanodine receptor to induce anesthesia in mice” by Hiroki R. Ueda et al., PLOS Biology
Abstract
Isoflurane activates the type 1 ryanodine receptor to induce anesthesia in mice
This study demonstrates that inhaled anesthetics directly activate RyR1, a calcium-release channel on the endoplasmic reticulum, and that this activation contributes to anesthetic and sedative effects in mice. Mutations at a single critical residue can abolish RyR1 sensitivity to isoflurane, and knock-in mice carrying such mutations resist behavioral loss of consciousness during isoflurane exposure. The work links molecular receptor activation to neuronal and behavioral responses and identifies RyR1-targeted compounds that produce sedation, supporting RyR1 as a functional mediator of volatile anesthetics.