Cannabinoid actions on sensitized dural nociceptors in a mouse migraine-like pain model
The 5th Annual MSC Emerging Science Contest for Early-Career Investigators took place on January 7, 2026. Below is a description of one of the presentations from the contest. (A recording of the event is available here).
Category: Migraine
Runner-up: Yoshihiro Kitaoka, PhD, UCLA
Title: Cannabinoid actions on sensitized dural nociceptors in a mouse migraine-like pain model.
Description: Migraine sensitization of trigeminal dural afferents occurs in a mouse model of migraine, and we hypothesize that peripherally-restricted cannabinoids (PRCBs) may be useful in suppressing behavioral symptoms caused by this sensitization. Anesthetized (isoflurane) female C57BL/6J mice (5-week-old) received supradural injections (at bregma) of pH 6.0 or pH 7.4 saline (5 μL). At 3 days post-injection, all mice were tested for latent sensitization by a second injection of pH 7.0 saline. Allodynia symptoms were assessed by withdrawal responses to stimulation of the periorbital region with calibrated von Frey hairs before and 1, 3, 5, 24, 48, and 72 hours after the 1st injection, and 1, 3, 5 and 24 hours after the 2nd injection. In separate groups of mice, the CB1R/CB2R agonist PRCB, PrNMI (5 μM), was co-applied with pH 6.0 saline with or without the peripherally-restricted selective CB1R inverse agonist, 18A (20 μM) or the brain permeant-selective CB2R inverse agonist, SR144528 (20 μM). Behavioral tests and recordings were performed by investigators blinded to the treatments.
Supradural co-administration of pH 6.0 saline with PrNMI prevented both the initial and latent symptoms of cutaneous allodynia. Co-administration of pH 6.0/PrNMI with 18A, or SR144528, abolished the preventative effects of PrNMI. Surprisingly, supradural co-administration of the potent CB2R-selective agonist RNB61 (5 µM) with pH 6.0 saline did not prevent the acid-induced allodynia or latent sensitization. Furthermore, post-treatment of PrNMI with pH 7.0 saline did not prevent latent allodynia. Patch clamp recordings were obtained from fluorogold-labeled dural afferent trigeminal ganglion neurons (dTGs) acutely isolated 3-days after fluorogold co-injection with pH 7.4 or pH 6.0 saline. In pH 6.0-treated mice, significantly greater depolarizing responses to acid stimulation were observed, indicating increased excitability. PrNMI (1 µM) significantly reduced acid responses in dTGs from pH 7.4-treated animals, but had no such effect in neurons from pH 6.0-treated animals, suggesting a loss of CB1R efficacy following acid-induced sensitization. Furthermore, in recordings from dTGs of pH 7.4-treated mice, RNB61 (1 µM) had no inhibitory effect on acid-induced depolarizations. These findings indicate that PrNMI prevents acid-induced sensitization by co-activating neuronal CB1Rs and non-neuronal CB2Rs. CB2R activation alone is insufficient, and once sensitized, combined CB1R/CB2R activation loses efficacy. This research highlights new potential treatments, such as PRCBs, which could prevent migraines and reduce their severity. Understanding these mechanisms may lead to better, more personalized care for patients, offering new options for both prevention and symptom relief.