Combined onabotulinumtoxinA/atogepant treatment blocks activation/sensitization of high-threshold and wide-dynamic range neurons

Abstract

Background: OnabotulinumtoxinA and agents that block calcitonin gene‒receptor peptide action have both been found to have anti-migraine effects, but they inhibit different populations of meningeal nociceptors. We therefore tested the effects of combined treatment with onabotulinumtoxinA and the calcitonin gene‒receptor peptide antagonist atogepant on activation/sensitization of trigeminovascular neurons by cortical spreading depression.

Material and methods: Single-unit recordings were obtained of high-threshold and wide-dynamic-range neurons in the spinal trigeminal nucleus, and cortical spreading depression was then induced in anesthetized rats that had received scalp injections of onabotulinumtoxinA 7 days earlier and intravenous atogepant infusion 1 h earlier. The control group received scalp saline injections and intravenous vehicle infusion.

Results: OnabotulinumtoxinA/atogepant pretreatment prevented cortical spreading depression-induced activation and sensitization in both populations (control: Activation in 80% of high-threshold and 70% of wide-dynamic-range neurons, sensitization in 80% of high-threshold and 60% of wide-dynamic-range neurons; treatment: activation in 10% of high-threshold and 0% of wide-dynamic-range neurons, sensitization in 0% of high-threshold and 5% of wide-dynamic-range neurons).

Discussion: We propose that the robust inhibition of high-threshold and wide-dynamic-range neurons by the combination treatment was achieved through dual blockade of the Aδ and C classes of meningeal nociceptors. Combination therapy that inhibits meningeal C-fibers and prevents calcitonin gene‒receptor peptide from activating its receptors on Aδ-meningeal nociceptors may be more effective than a monotherapy in reducing migraine days per month in patients with chronic migraine.

Keywords: CGRP; Migraine; cortical spreading depression; headache; meningeal nociceptor; trigeminal.

Figure 1.

Experimental design. Treatment group received onabotulinumtoxinA injections to the scalp and intravenous atogepant. Control group received saline injections to the scalp and intravenous infusion of vehicle (50% dextrose water, 40% PEG 400, and 10% tocopherol). The star indicates the time at which responses to mechanical stimulation of the dura and skin were measured. ATO: atogepant; BoNT-A: onabotulinumtoxinA; CSD: cortical spreading depression; IV: intravenous; PEG: polyethylene glycol.

Figure 2.

Recording sites ((a),(b)) and dural ((c),(d)) and facial ((e),(f)) receptive fields of all studied HT and WDR trigeminovascular neurons. Black and gray circles depict locations of lesions of HT and WDR neurons in the different laminae of the upper cervical spinal cord segment. Red indicates locations and sizes of most sensitive areas of dural and cutaneous receptive fields. Inset in (c) depicts dural receptive field drawings. HT: high threshold; WDR: wide-dynamic range.

Figure 3.

CSD effects on activation and sensitization of HT neurons in treated and untreated animals. (a) Plots of firing rate before (blue) and after (red) CSD induction in an animal treated with saline and vehicle (control). Note that spontaneous firing and responses to mechanical stimulation of the dura and skin increased after the CSD. (b) Plots of firing rate before (blue) and after (green) CSD induction in an animal treated with the combination of onabotulinumtoxinA and atogepant (treatment group). Note that spontaneous activity and responses to stimulation of the dura and skin did not increase after the CSD. Recording sites and locations of dural and cutaneous receptive fields are shown on the right. CSD: cortical spreading depression; HT: high threshold; VFH: von Frey hair.

Figure 4.

Percentage of neurons activated by CSD after combination treatment of onabotulinumtoxinA and atogepant (treatment group) or saline and vehicle (control) in HT (a), WDR (b) and all neurons (c). Chi square (χ²) was used to calculate the level of significance of the percentage differences between the groups. CSD: cortical spreading depression; HT: high threshold; WDR: wide-dynamic range.

Figure 5.

Changes from baseline in spontaneous activity at 1 and 2 h after CSD induction, shown in box-and-whisker plots combined with scatterplots of individual values, for control (in red; (a), (c), (e)) and treatment (in blue; (b), (d), (f)) groups. (a) and (b) HT neurons (n = 10 per group); (c) and (d) WDR neurons (n = 10 per group); (e) and (f) all neurons (n = 20 per group). *p < 0.05 Friedman test; post-hoc/Tukey HSD. CSD: cortical spreading depression; HT: high threshold; WDR: wide-dynamic range.

Figure 6.

Changes from baseline in response to dural indentation at 1 and 2 h after CSD induction, shown in box-and-whisker plots combined with scatterplots of individual values, for control (in red; (a), (c), (e)) and treatment (in blue; (b), (d), (f)). (a) and (b) HT neurons (n = 10 per group); (c) and (d) WDR neurons (n = 10 per group); (e) and (f) all neurons (n = 20 per group). *p < 0.05 Friedman test; post-hoc/Tukey HSD. CSD: cortical spreading depression; HT: high threshold; WDR: wide-dynamic range.

Figure 7.

Changes from baseline in responses to mechanical stimulation of the skin (I. brush, II. pressure, and III. pinch) at 1 and 2 h after CSD induction, shown in box-and-whisker plots combined with scatterplots of individual values, for control (in red; (a),(c),(e)) and treatment (in blue; (b),(d),(f)). (a) and (b) HT neurons (n = 10 per group); (c) and (d) WDR neurons (n = 10 per group); (e) and (f) all neurons (n = 20 per group). *p < 0.05 Friedman test; post-hoc/Tukey HSD. CSD: cortical spreading depression; HT: high threshold; WDR: wide-dynamic range.

Figure 8.

CSD effects on activation and sensitization of WDR neurons in treated and untreated animals. (a) Plots of firing rate before (blue) and after (red) CSD induction in an animal treated with saline and vehicle (control). Note that spontaneous firing and responses to mechanical stimulation of the dura and skin increased after the CSD. (b) Plots of firing rate before (blue) and after (green) CSD induction in an animal treated with the combination of onabotulinumtoxinA and atogepant (treatment group). Note that spontaneous activity and responses to stimulation of the dura and skin did not increase after the CSD. Recording sites and locations of dural and cutaneous receptive fields are shown on the right. CSD: cortical spreading depression; WDR: wide-dynamic range.