α6GABAA Receptor Positive Modulators Alleviate Migraine-like Grimaces in Mice via Compensating GABAergic Deficits in Trigeminal Ganglia

Abstract

Migraine is caused by hyperactivity of the trigeminovascular system, where trigeminal ganglia (TG) play an important role. This hyperactivity might originate from an underfunctional GABAergic system in TG. To investigate this possibility, we adapted a mouse model of migraine by inducing migraine-like grimaces in male mice via repeated injections of nitroglycerin (NTG, 10 mg/kg, i.p.), once every 2 days, for up to 5 sessions. Migraine-like facial pain scores were measured using the mouse grimace scale. Repeated NTG treatments in mice caused significant increases in migraine-like grimaces that were aborted and prevented by two anti-migraine agents sumatriptan and topiramate, respectively. After 5 sessions of NTG injections, the GABAsynthesizing enzyme, 65-kDa glutamate decarboxylase (GAD65), but not the GABA transporter 1 (GAT1) or the α6 subunitcontaining GABA A receptors (α6GABA A Rs), was downregulated in mouse TG tissues. Taking advantage of the unaffected TG α6GABA A R expression in NTG-treated mice, we demonstrated that an α6GABA A R-selective positive allosteric modulator (PAM), DK-I-56-1, exhibited both abortive and prophylactic effects, comparable to those of sumatriptan and topiramate, respectively, in this migraine-mimicking mouse model. The brain-impermeable furosemide significantly prevented the effects of DK-I-56-1, suggesting its peripheral site of action, likely via preventing α6GABA A R modulation in TG. Results suggest that a decreased GABA synthesis caused by the reduced GAD65 expression in TG contributes to the trigeminovascular activation in this repeated NTG-induced migraine-mimicking model and that the unaltered α6GABA A Rs in TG are potential targets for migraine treatment. Thus, α6GABA A R-selective PAMs are potential anti-migraine agents for both abortive and preventive therapies.Key Words Migraine . α6 subunit-containing GABA A receptor . trigeminal ganglia . nitroglycerin . mouse grimacescale . 65-kDa glutamate decarboxylase . GABA transporter 1.Hung-Ruei Tzeng and Ming Tatt Lee contributed equally to this work.

Positive modulation of cerebellar α6GABAAreceptors for treating essential tremor: a proof-of-concept study in harmaline-treated mice

“…The effective dose range (3-10 mg/kg, i.p.) of Compound 6 in suppressing tremor was similar to that in mouse models of schizophrenia (Chiou et al, 2018;Chiou et al, 2019) and migraine (Tzeng et al, 2020). At these doses, Compound 6 did not impair motor functions in rats (Knutson et al, 2018), nor display sedative (Wu and Chiou, 2016) or hypolocomotor activity (Chiou (which was not certified by peer review) is the author/funder.…”

“…We have previously demonstrated that Compound 6, one of the first α6GABAAR-selective PAMs identified (Knutson et al, 2018;Varagic et al, 2013), via acting at cerebellar α6GABAARs, ameliorated disrupted prepulse inhibition (PPI) of the startle response (Chiou et al, 2018), social withdrawal and cognitive impairment (Chiou et al, 2019) in animal models mimicking schizophrenia. By acting via α6GABAARs at trigeminal ganglia, it inhibited nociceptive activation of the trigeminovascular system and migraine-like grimaces in animal models of migraine (Fan et al, 2018;Tzeng et al, 2020). And, a deuterated Compound 6 analogue, DK-I-56-1, prevented and reduced trigeminal neuropathic pain in a rat model (Vasovic et al, 2019).…”

Dorsal root ganglia control nociceptive input to the central nervous system

“…Transcript levels of enzymes (GAD65, GAD67) and transporters (VGAT) needed to synthesize and package GABA into vesicles are low according to transcriptomic studies (53,54). Yet functional proteins are detectable (15,23,55), as is tonic and induced GABA release (Fig. 7 and ( 15)).…”

Deep Learning-Based Grimace Scoring Is Comparable to Human Scoring in a Mouse Migraine Model

“…All the study data were obtained from our previous study [ 22 ], where all animal experiments were approved by the Institutional Animal Care and Use Committee of National Taiwan University, College of Medicine, Taipei, Taiwan and were consistent with the national guidelines. Male mice (ICR strain, 8–10 weeks old, 30–35 g) were used in the experiments.…”

“…We used a mouse migraine model induced by repeated and intermittent injections of NTG and a control group injected with saline [ 21 ]. The migraine-like painful facial expressions in mice were video-recorded and scored using the MGS [ 22 ]. Mouse facial images were classified as the NTG condition, saline condition, and preinjection condition.…”