Tracking changes in glutamate in response to prolonged noxious stimulation

Objectively measuring pain has proven challenging, largely due to the subjective and multidimensional nature of pain. There is a pressing need to identify valid outcome measures to evaluate treatment modalities for individuals suffering from pain. Current treatment and diagnosis of pain conditions, are dependent on self-report measures. A critical limitation is the lack of mechanistic information from this measure. The objective of this thesis was to examine potential biochemical biomarkers that account for the variability of pain perception among healthy individuals. Specifically, to examine changes in excitatory neurotransmitter concentrations (glutamate and Glx: glutamate+glutamine) in the anterior cingulate cortex (ACC) using functional single voxel magnetic resonance spectroscopy during an in-scanner noxious intervention. Excitatory neurotransmitter values were quantified every 2 minutes, simultaneously, the rating of perceived pain intensity was recorded (using a 0-10 numeric rating scale) to examine the relationship of glutamate levels and pain perception. Results show individuals with higher baseline glutamate values report higher pain ratings, however when tracked dynamically no relationship is seen between glutamate (or Glx) levels and ratings of perceived pain intensity with the current methodology. While further research is needed, baseline glutamate values may prove useful in pre-treatment identification. For example, in clinical trials classifying high and low pain responders based on glutamate baseline values may provide insight into the variability of treatment responders.Education, Faculty ofKinesiology, School ofGraduat