NON-INVASIVE VAGAL NERVE STIMULATION REDUCES THE AMOUNT OF EXTRACELLULAR GLUTAMTE IN THE TRIGEMINAL NUCLEUS CAUDALIS AFTER AN INJECTION OF GLYCEROL TRINITRATE IN RATS
H Hekierski Jr., M Oshinsky Department of Neurology, Jefferson Headache Center, Thomas Jefferson University, Philadelphia, PA, USA
Vagal nerve stimulation has been used to treat seizures and depression and is now being developed to treat migraine. The goal of this study was to determine if non-invasive vagal nerve stimulation (nVNS) could be used to abort an increase in trigeminal allodynia in rats. Rats were transitioned into experiencing low trigeminal mechanical allodynia thresholds following repeated infusions of prostaglandin directly against the dura. Microdialysis was used to quantify levels of neurotransmitters in the trigeminal nucleus caudalis (TNC) in rats using high performance liquid chromatography (HPLC). Rats with low trigeminal thresholds experience a seven-fold increase in extracellular glutamate within the TNC when administered an IP injection of glycerol trinitrate (GTN; 0.1mg/kg), during microdialysis. In this study rats were injected with GTN and then two hours later nVNS was conducted in order to lower the glutamate levels, which simulates a human patients using nVNS to reduce their own migraine. Testing revealed that GTN treatment was able to increase extracellular glutamate to 6.26±0.911 fold the baseline (n=5) in the TNC. After a period of two hours nVNS was conducted and extracellular glutamate deceased to 2.51±0.297 (n=5) the original baseline and remained there until the experiment concluded. To further prove that nVNS is able to treat headaches the mechanism of action of nVNS must be discovered.