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Spontaneous activity in dorsal root ganglion (DRG) neurons is a key driver of neuropathic pain in patients suffering from this largely untreated disease. While many intracellular signalling mechanisms have been examined in preclinical models that drive spontaneous activity, none have been tested directly on spontaneously active human nociceptors. Using cultured DRG neurons recovered during thoracic vertebrectomy surgeries, we showed that inhibition of mitogen-activated protein kinase interacting kinase (MNK) with tomivosertib (eFT508, 25 nM) reversibly suppresses spontaneous activity in human sensory neurons that are likely nociceptors based on size and action potential characteristics associated with painful dermatomes within minutes of treatment. Tomivosertib treatment also decreased action potential amplitude and produced alterations in the magnitude of after hyperpolarizing currents, suggesting modification of Na+ and K+ channel activity as a consequence of drug treatment. Parallel to the effects on electrophysiology, eFT508 treatment led to a profound loss of eIF4E serine 209 phosphorylation in primary sensory neurons, a specific substrate of MNK, within 2 min of drug treatment. Our results create a compelling case for the future testing of MNK inhibitors in clinical trials for neuropathic pain. [ABSTRACT FROM AUTHOR]

The serotonergic system has long been linked to migraine but recent studies highlight how much is still unclear about this link. And recent data add to the uncertainty of where/how triptans act and why they are headache specific.Markers of 5HT levels in the brains of migraine patients show no changes between attacks. Several recent meta-analyses show the most convincing data on genetic differences in the serotonergic system for 5HT transporters. Findings of additional triptan actions on peripheral trigeminovascular neurons and in the hypothalamus add more fuel to the debate on where these drugs act. A growing list of studies show efficacy of multiple triptans and other 5HT1b/1d agonists in preclinical models of nonheadache pain arguing for reevaluation of whether these drugs have efficacy in other pain states. Despite these issues, serotonergic drugs continue to be the gold standard for abortive agents with new members on the horizon (5HT1f agonists).Given the clear efficacy of serotonergic drugs for migraine, continued study on the role of the endogenous 5HT system may lead to more novel therapies. And with the list of studies demonstrating efficacy triptans in models of nonheadache, clinical studies should address whether these drugs work for other types of pain. [ABSTRACT FROM AUTHOR]

Background: Migraine is characterized by a collection of neurological symptoms in the absence of injury or damage. However, several common preclinical migraine models require significant damage to the skull to stimulate the dura mater, the likely source of afferent signaling leading to head pain. The goal of this study was to determine whether dural stimulation can be performed in mice using an injection that does not cause injury or damage.Methods: Using mice, injections of stimuli were administered to the dura mater through the soft tissue at the intersection between the lambdoidal and sagittal sutures. This technique did not require a permanent cannula nor did it cause damage to the skull or dura. Following injection of noxious stimuli, migraine-like behaviors were measured including cutaneous allodynia and facial grimace. The retrograde tracer fluorogold was applied onto the dura using the same injection technique to label trigeminal ganglion cell bodies, which were then testing in vitro using patch-clamp electrophysiology.Results: Dural injection of allyl-isothiocyanate, low pH, interleukin-6, or inflammatory soup but not vehicles, led to cephalic/extracephalic allodynia. Facial grimace responses were also observed with allyl-isothiocyanate, pH 6.0, and interleukin-6. Stimulation with interleukin-6 causes priming to normally subthreshold pH 7.0 stimulation of the dura following resolution of the initial interleukin-6 behavior. Systemic injection of sumatriptan at the time of dural stimulation with inflammatory soup decreased the resulting cutaneous hypersensitivity. Trigeminal ganglion cell bodies retrogradely labeled from the dura had low pH-evoked currents similar to those generated by acid-sensing ion channels.Conclusion: Non-invasive dural stimulation in mice can be used as a model of migraine in the absence of injury. [ABSTRACT FROM AUTHOR]

Spontaneous activity in dorsal root ganglion (DRG) neurons is a key driver of neuropathic pain in patients suffering from this largely untreated disease. While many intracellular signalling mechanisms have been examined in preclinical models that drive spontaneous activity, none have been tested directly on spontaneously active human nociceptors. Using cultured DRG neurons recovered during thoracic vertebrectomy surgeries, we showed that inhibition of mitogen-activated protein kinase interacting kinase (MNK) with tomivosertib (eFT508, 25 nM) reversibly suppresses spontaneous activity in human sensory neurons that are likely nociceptors based on size and action potential characteristics associated with painful dermatomes within minutes of treatment. Tomivosertib treatment also decreased action potential amplitude and produced alterations in the magnitude of after hyperpolarizing currents, suggesting modification of Na+ and K+ channel activity as a consequence of drug treatment. Parallel to the effects on electrophysiology, eFT508 treatment led to a profound loss of eIF4E serine 209 phosphorylation in primary sensory neurons, a specific substrate of MNK, within 2 min of drug treatment. Our results create a compelling case for the future testing of MNK inhibitors in clinical trials for neuropathic pain., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)