Key result
Fentanyl directly blocks a subset of EAG-class potassium channels, causing paradoxical excitation of cervical spinal motoneurons and persistent tonic diaphragmatic muscle activity.
Why the study?
Fentanyl uniquely triggers respiratory muscle rigidity known as Wooden Chest Syndrome, but the underlying mechanisms are poorly understood.
Fentanyl directly blocks EAG-class potassium channels, causing paradoxical excitation of respiratory motoneurons and tonic diaphragmatic muscle activity, revealing a novel mechanism for Wooden Chest Syndrome.
This is the authors' abstract. We don't add key points for this paper.
Fentanyl is a potent synthetic opioid widely used perioperatively and illicitly as a drug of abuse 1,2 . It is well established that fentanyl acts as a μ-opioid receptor agonist, signaling through Gα i/o intracellular pathways to inhibit electrical excitability, resulting in analgesia and respiratory depression 3,4 . However, fentanyl uniquely also triggers muscle rigidity, including respiratory muscles, hindering the ability to execute central respiratory commands or to receive external resuscitation. This potentially lethal condition is termed Wooden Chest Syndrome (WCS), the mechanisms of which are poorly understood 5–7 . Here we show that fentanyl directly blocks a subset of EAG-class potassium channels 8 . Our results also demonstrate that these channels are widely expressed in cervical spinal motoneurons, including those innervating the diaphragm. A significant fraction of these motoneurons is excited by fentanyl, concomitant with blockade of voltage-dependent non-inactivating K + currents . In vivo electromyography revealed a persistent tonic component of diaphragmatic muscle activity elicited by fentanyl, but not morphine. Taken together our results identify a novel off-target mechanism for fentanyl action, independent of μ-opioid receptor activation, with a paradoxical excitatory effect that may underlie WCS. We anticipate these findings may inform the design of safer analgesics and generalize to other neuronal circuits implicated in fentanyl-related maladaptive behaviors.
Alerts to rigidity as fentanyl risk beyond respiratory depression; hypothesis-generating for targeted interventions in perioperative and abuse settings.
No takes yet. Share an insight, caveat, or question.
Wei et al. (2025) studied Wooden Chest Syndrome. Fentanyl vs. Morphine or baseline was evaluated on Blockade of EAG-class potassium channels and tonic diaphragmatic muscle activity. Fentanyl directly blocks a subset of EAG-class potassium channels, causing paradoxical excitation of cervical spinal motoneurons and persistent tonic diaphragmatic muscle activity.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: