Connexin 36 Mediates Orofacial Pain Hypersensitivity Through GluK2 and TRPA1

Trigeminal neuralgia is a debilitating condition,and the pain easily spreads to other parts of the face.Here,we established a mouse model of partial transection of the infraorbital nerve(pT-ION)and found that the Connexin 36(Cx36)inhibitor mefloquine caused greater alleviation of pT-ION-induced cold allodynia compared to the reduction of mechanical allodynia.Mefloquine reversed the pT-IONinduced upregulation of Cx36,glutamate receptor ionotropic kainate 2(GluK2),transient receptor potential ankyrin 1(TRPA1),and phosphorylated extracellular signal regulated kinase(p-ERK)in the trigeminal ganglion.Cold allodynia but not mechanic al allodynia induced by pT-ION or by virusmediated overexpression of Cx36 in the trigeminal ganglion was reversed by the GluK2 antagonist NS 102,and knocking down Cx36 expression in Nav1.8-expressing nociceptors by injecting virus into the orofacial skin area of Nav1.8-Cre mice attenuated cold allodynia but not mechanic al allodynia.In conclusion,we show that Cx36 contributes greatly to the development of orofacial pain hypersensitivity through GluK2,TRPA1,and p-ERK signaling.

Short-term effects of repetitive transcranial magnetic stimulation on sleep bruxism-a pilot study

The purpose of this study was to investigate the effects of repetitive transcranial magnetic stimulation （rTMS） on patients with sleep bruxism （SB）. Twelve patients with SB were included in an open, single-intervention pilot study, rTMS at 1 Hz and an intensity of 80% of the active motor threshold was applied to the ‘hot spot＇ of the masseter muscle representation at the primary motor cortex bilaterally for 20 rain per side each day for 5 consecutive days. The jaw-closing muscle electromyographic （EMG） activity during sleep was recorded with a portable EMG recorder at baseline, during rTMS treatment and at follow-up for 5 days. In addition, patients scored their jaw-closing muscle soreness on a 0-10 numerical rating scale （NRS）. Data were analysed with analysis of variance. The intensity of the EMG activity was suppressed during and after rTMS compared to the baseline （P = 0.04; P = 0.02, respectively）. The NRS score of soreness decreased significantly during and after rTMS compared with baseline （P 〈 0.01）. These findings indicated a significant inhibition of jaw-closing muscle activity during sleep along with a decrease of muscle soreness. This pilot study raises the possibility of therapeutic benefits from rTMS in patients with bruxism and calls for further and more controlled studies.

Burning Mouth Syndrome

Most clinicians dread seeing the patient presenting with a primary complaint of a burning pain on one or more oral mucosal surfaces. Unlike most other clinical conditions presenting in a dental office, burning mouth syndrome is poorly understood with few evidence based remedies. More recently, advances have been made towards clarifying the possible etiology of the disorder and testing the possible therapeutic modalities available. This article attempts to summarize the ＂state of the art＂ today.

Acupuncture Treatment for Idiopathic Trigeminal Neuralgia:A Longitudinal Case-Control Double Blinded Study

Objective： To evaluate the treatment effect of acupuncture on patients with idiopathic trigeminal neuralgia（ITN） by case-control longitudinal blinded study. Methods： Sixty ITN patients and 30 healthy subjects were included. The ITN patients were randomly assigned to acupuncture group（15 cases）, sham-acupuncture group（15 cases） and carbamazepine group（30 cases）, respectively. Clinical orofacial evaluation（including pain intensity and medication doses）, research diagnostic criteria for temporomandibular disorders（RDC/TMD） and Helkimo indexes（for functional evaluation of the masticatory system）, and quantitative sensory testing for sensory thresholds（gustative, olfactory, cold, warm, touch, vibration and superficial and deep pain） were evaluated before treatment, immediately after treatment, and 6 months after treatment. Results： The mean pain intensity by the Visual Analogue Scale only decreased in the acupuncture group at the last evaluation（P=0.012）. Patients in the sham-acupuncture group had an increase in carbamazepine doses according to the prescriptions（P〈0.01）. There was a reduction in secondary myofascial pain and mandibular limitations at the acupuncture and sham-acupuncture groups, however only the acupuncture group kept the changes after 6 months（P〈0.01, P=0.023）. There was a decrease in mechanical thresholds in the acupuncture group（tactile, P〈0.01; vibration, P=0.027） and an increase in deep pain thresholds in both acupuncture and sham-acupuncture groups（P=0.013）. Conclusion： Acupuncture can be an option in the treatment of ITN due to its analgesic effect in both ITN and secondary myofascial pain associated with it.