Brian Cairns

 
Prospective Graduate Students / Postdocs

This faculty member is currently not actively recruiting graduate students or Postdoctoral Fellows, but might consider co-supervision together with another faculty member.

Professor

Research Classification

Neuropharmacology
Oro-Facial Pain
Pain
Electrophysiology

Research Interests

pain mechanisms
headache
temporomandibular disorders
sex-related differences
peripheral analgesics

Relevant Degree Programs

 

Research Methodology

In vivo electrophysiology
In vivo pharmacology
immunohistochemistry

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2019)
The role of peripheral NMDA receptors in nerve growth factor-induced muscle pain (2015)

Intramuscular injections of nerve growth factor (NGF) into human masseter muscle induce a local mechanical sensitization that mimics the symptoms of myofascial pain in patients with temporomandibular disorders. I hypothesize that NGF induces the myofascial mechanical sensitization in part by increasing the expression of N-methyl-D-aspartate (NMDA) receptors in primary afferent neurons. In behavioral experiments, injection of NGF into rat masseter muscle induced a prolonged local mechanical sensitization that was greater in female rats than in male rats. This NGF-induced sensitization was partly attenuated by a local injection of the NMDA receptor antagonist APV at 3 days post NGF injection in the male rats but not in the female rats. Immunohistochemical studies found that this NGF-induced mechanical sensitization was accompanied by the increased expression of NMDA receptor subtype 2B (NR2B) in trigeminal ganglion neurons innervating the masseter muscle in both sexes, as well as an increase in the average soma size of NR2B-expressing neurons. An increase in the expression of neuropeptides (CGRP/SP) was also observed in the female rats but not in the male rats. In in vivo extracellular recordings of masseter trigeminal ganglion neurons, NGF increased NMDA-induced mechanical sensitization in the male rats but not in the female rats. However, in the female rats, this effect was greater in slow Aδ fibers (2-7 m/s) than fast Aδ fibers (>7-12 m/s). My results suggest that NGF-induced mechanical sensitization is mediated, in part, through an effect on peripheral NMDA receptors in a sexually dimorphic manner.

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Tumor necrosis factor alpha and non-inflammatory sensitization of masseter muscle nociceptors (2011)

Behavioral evidence in rats indicates that injection of tumor necrosis factor alpha (TNFalpha into skeletal muscle results in a prolonged mechanical sensitization without gross inflammation. The present series of studies were conducted to test the idea that injection of TNFalpha causes mechanical sensitization of skeletal muscle through a peripheral mechanism that involves lowering of the mechanical threshold (MT) of muscle nociceptors without inflammation. In- vivo extracellular electrophysiological recording was used to assess the effect of TNFalpha (1 or 0.1microgram) and other drugs on the excitability and MT of masseter muscle nociceptors. Expression of TNFR1 (P55) and TNFR2 (P75) receptors by the masseter muscle and trigeminal ganglion neurons that innervate that muscle was determined by Western blot and immunohistochemical methodologies, respectively. The Evans blue dye technique and thermal camera recordings were used to assess inflammation in muscle tissues. Enzyme-linked immunoassays and glutamate biosensor probes were used to measure muscle concentrations of prostaglandin (PG) E2 and nerve growth factor, and glutamate, respectively. Intramuscular injection of 1mg TNFalpha did not excite nociceptors, but did significantly decrease MT compared to vehicle control. There was no evidence of gross inflammation 3 hours after injection of TNFalpha. Co-injection of TNFalpha with P55 or P75 receptor antibodies attenuated TNFalpha-induced mechanical sensitization. P55 and P75 receptors were expressed by 29% and 62% of masseter nociceptors, respectively. PGE2 and glutamate concentrations were significantly changed 3 hours after TNFalpha injection into the masseter muscle. Injection of diclofenac, a cycloxygenase inhibitor that attenuates prostaglandin synthesis, partially reversed the TNFalpha-induced decreases in the MT of masseter muscle nociceptors, while vehicle control, DL-2-amino-5-phophonovaleric acid, a competitive NMDA receptor antagonist, and a tyrosine kinase A receptor antibody, which blocks NGF-induced masseter muscle nociceptor sensitization, did not significantly alter nociceptor MT. These findings indicate that TNFalpha-induced mechanical sensitization of masseter nociceptors is mediated, in part, by increased PGE2 levels through activation of peripheral P55 and P75 receptors. Over all, these results suggest that injection of TNFalpha into skeletal muscle could be used as a model of myofascial trigger points to study the peripheral pain mechanisms of masticatory muscle pain.

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Master's Student Supervision (2010 - 2018)
The role of monosodium glutamate in headache (2016)

Consumption of monosodium glutamate (MSG) can induce headache in young healthy individuals and migraine-like headache in migraineurs. Blood plasma levels of glutamate are also elevated in migraineurs, but it is unknown how elevated levels of glutamate contribute to headache. The current study was undertaken to investigate the hypothesis that monosodium glutamate induces headache through activation of peripheral glutamate receptors. To test the hypothesis, we combined in vivo electrophysiology, laser Doppler recordings of dural vasculature, and immunohistochemistry to investigate the effect of systemic administration of MSG on the trigeminovascular pathway. Immunohistochemical analysis of the dura, determined that the nerve fibres innervating dural blood vessels express NMDA, AMPA, kainate and mGlur5 receptors. The glutamate transporter EAAT2, but not EAAT1 or 3, is expressed by dural blood vessels. Systemic administration of 50mg/kg MSG induced a 24.5 and 20.6 percent increase in dural blood flow in male and female rats, respectively, as measured by laser Doppler flowmetry. Dural blood flow returned to baseline values by a mean of 170 seconds. In in vivo extracellular recordings of spinal trigeminal subnucleus caudalis (SpVc) neurons with dural receptive fields, intravenously administered MSG evoked an increase in neuronal discharge in 5/6 neurons in both male and female rats. MSG also induced mechanical sensitization in both sexes. When the NMDA receptor selective antagonist APV (5, 50mg/kg) was co-administered with MSG, it attenuated both the MSG evoked activation and mechanical sensitization of SpVc neurons. Myresults suggest that MSG induced headache is mediated, in part, through activation of the peripheral NMDA receptor.

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Peripheral mechanisms of masseter muscle nociceptor sensitization by Nerve Growth Factor (NGF) (2010)

No abstract available.

Current Students & Alumni

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