171 An Investigation of the Effects of Subthalamic Deep Brain Stimulation on Thermal and Mechanical Thresholds in Parkinsonian Rats. Issue Volume 61:Issue CN Supp. 1(2014)Supplement (1st August 2014) - Gee, Lucy
Abstract: INTRODUCTION: Subthalamic deep brain stimulation (STN-DBS) is a highly effective treatment for motor symptoms of Parkinson disease (PD). As motor symptom treatment improves, non-motor symptoms of PD are highlighted. Currently, 65% to 80% of PD patients suffer from chronic pain. Significant decreases are found in sensory thresholds of PD patients compared to controls. Rodent models of PD show decreased mechanical, thermal and chemical thresholds. Further, patients tested ON and OFF STN-DBS have higher thresholds while ON stimulation. STN-DBS is analgesic in a significant number of patients, reducing pain 3 to 6 months after surgery to tolerable levels; however, the mechanism of this is unclear. It has been well established that basal ganglia play a large role in movement initiation, and recent evidence indicates it may also play a role in sensory processing. To identify the mechanism, we begin by demonstrating STN-DBS improves sensory processing in a PD rat. METHODS: Bilateral STN-DBS was implanted in rats with 6OHDA induced parkinsonism. Sensory thresholds were tested using von-frey (VF) filaments as well as the hot plate (HPT) and tail flick (TFT) tests. We tested ON and OFF high (HFS) and low (LFS) frequency stimulation to determine changes in sensory thresholds. RESULTS: PD rats had lower mechanical and thermal thresholds than naïve when tested using VF (bilaterally P < .001), HPT ( P = .0117) and TFT ( P = .0132). LFS significantly improved mechanical thresholds in the left paw ( P = .028). No significant changes were found to mechanical stimuli after HFS; however, the overall effect of stimulation in PD animals tended to improve ( P = .077). Finally, no changes in thermal thresholds were seen at HFS or LFS. CONCLUSION: PD rats are sensitive to both thermal and mechanical stimuli. Our preliminary results suggest LFS modulates mechanical thresholds, but not thermal ones. HFS produced no significant effects. We acknowledge our small sample size and further investigation into STN-DBS is necessary.