| Background:Migraine is a complicated neurological disorder.Migraine is characterized by attacks of throbbing head pain,accompanied by nausea,vomiting,photophobia.It usually is sensitivity to movement,visual,auditory,and other afferents inputs.In addition to headache,non-headache symptoms,such as vestibular dysfunction,are also common.Up to 51.7-76%of migraine patients have described the onset of vestibular symptoms.Migraine with vestibular symptoms is more disabling and more likely to be combined with other complications,including insomnia and depression,which can lead to worse treatment outcomes,reduced social functioning and greater financial burden.However,little is known about the pathophysiology of vestibular symptoms associated with migraine.Due to the limitations of preclinical models,the mechanism of migraine-related vestibular impairment still relies on the study of migraine itself.The purpose of this study was to investigate the role of Glu TNC-VN neural circuits in migraine related vestibular dysfunction.Methods:1.We first evaluated the behavioral changes after inducing CM rat model.Rats were subjected to a CM model and received intraperitoneal nitroglycerin（NTG）every other day for 9 days（5 times in total）.2.We injected retrograde tracer FG and anterograde tracer virus H129-G4 by brain stereotaxic injection method into the VN and TNC sites（n=3/group）of healthy rats,respectively.3.Next we determined the necessity of TNC activity for vestibular function by chemogenetically inhibiting TNC glutamatergic neurons with AAV encoding engineered Gi-coupled h M4D receptor（AAV-Ca MKIIα-h M4D-m Cherry）.We examined pain-and vestibular function-related behavioral tests in rats.4.To further investigate the role of the TNC-VN pathway in migraine associated vestibular dysfunction,we used chemogenetic methods to inhibit TNC-VN projection neurons.For chemogenetic inhibition of TNC-projecting VN neurons,retrograde transport Cre recombinase AAVretro-Syn-Cre was injected unilaterally into the VN and Cre-dependent AAV-EF1α-DIO-h M4D-m Cherry was unilaterally injected into the TNC,and the two injection sites were on the same side.5.We used whole-cell patch clamp in VN neurons to detect whether inhibiting TNC glutamatergic neurons could change miniature excitatory postsynaptic currents（m EPSCs）.Result1.Recurrent administration of NTG induced migraine-like behaviors and vestibular dysfunction.2.By using anterograde and retrograde tracers,we verified the anatomic pathway of TNC projection to VN.Further immunofluorescence results showed that glutaminergic neurons were the main types of trigeminal and vestibular neurons under physiological conditions.TNC neurons terminated onto CGRP-ir neurons within the VN.3.Inhibition of TNC glutaminergic neurons can reduce the activation of VN neurons.Behavioral results showed that inhibition of TNC glutaminergic neurons could alleviate hyperalgesia and vestibular dysfunction in CM rats.4.Specific inhibition of TNC-VN neural circuit by chemogenetic method can reverse migraine related hyperalgesia and vestibular dysfunction in rats.5.Whole cell patch clamp recording showed that chemogenetic inhibition of glutamatergic TNC neurons reduced the frequency of miniature excitatory postsynaptic currents（m EPSCs）through a presynaptic mechanism in vestibular nucleus（VN）slice preparations but showed no effect on the amplitude.ConclusionsIn summary,our results demonstrated that TNC glutamatergic neurons alter CGRP+TNC-projecting VN neurons via a presynaptic mechanism involved in migraine-related vestibular dysfunction.Our findings may provide new insights for treatment of the migraine-related vestibular symptoms. |
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