OK, thank you very much. Our next abstract presenter is Miriam Hsiao, who's going to be presenting on subthalamic nucleus DBS combined with duloxetine changes pain behavior in Parkinsonian rats. Hi, everyone. I'm Miriam Hsiao, and I'm a medical student and working in Dr. Julie Politsis' lab. Here are our disclosures. So chronic pain is the most common non-motor symptom of Parkinson's disease, and it is undertreated in more than 50% of cases. Current pharmacological treatments, such as L-DOPA or monoamine reuptake inhibitors, are limited in their efficacy. And recently, it has been shown that subthalamic nucleus D brain stimulation, or STN-DBS, provides pain relief to these PD patients. And STN-DBS is already FDA-approved to treat the motor symptoms of PD. However, this can be optimized because a recent study has shown that 74% of patients receiving STN-DBS developed new pain symptoms eight years post-op. As Brian mentioned in his talk, data has shown that Bonfray filament mechanical threshold tests have shown that high frequency STN-DBS combined with duloxetine, or STN-DBS duloxetine, increases mechanical thresholds significantly more than STN-DBS alone or duloxetine alone. So this data suggests that STN-DBS duloxetine decreases nociception, but there's a difference between nociception and pain. Nociception refers to the sensory detection of noxious stimuli, but pain refers to the multifaceted experience that involves emotion, memory, and higher cognitive processes. Therefore, the effects of STN-DBS duloxetine on pain remain unknown. The goals of this study were to transition from assessing STN-DBS duloxetine's effect on nociception to pain by measuring escape avoidance behavior in Parkinsonian rats. Now, escape avoidance behavior was chosen as a measure of pain-related behavior because it is included in the well-validated pain anxieties symptom scale. So our hypothesis was that STN-DBS duloxetine reduces escape avoidance behavior more than STN-DBS or duloxetine alone in Parkinsonian rats. So 6-hydroxydopamine was injected into the right medial forebrain bundle of rats. They were given 2 weeks recovery period before LAT testing was done for, to assess for PD motor symptoms and von Frey filament mechanical threshold testing was done to assess for neuropathy. If the rat had both the PD motor symptoms and neuropathy, they were then progressed to receiving their first place escape avoidance paradigm test. And this, I will be referring to this as the PIAT test. They then received treatment for 3 consecutive days. Treatment consisted of either STN-DBS duloxetine, STN-DBS alone, or duloxetine alone. And STN-DBS was delivered through an external stimulator into an electrode for 30 minutes. And this electrode had been stereotoxically implanted into the STN. On their third day after their last treatment, the rats then received their second PIAT test. They then underwent perfusion and their brain tissue was collected for tyrosine hydroxylase and crucial violet staining. So the PIAT test was done to assess for escape avoidance behavior. And as mentioned before, assessing escape avoidance behavior is important because it is included as a measure of pain-related behavior in the pain anxiety symptom scale. And what happens in this test is a rat is placed in a PIAT chamber that is shown in the slide. And the chamber consists of a bright side and a dark side that are both easily accessible to the rat. During a test session, the rat is poked with a mechanical superthreshold von Frey filament every 15 seconds for 30 minutes. When a rat spends time in the dark side, they are poked on their left Parkinsonian neuropathy-affected paw. And whenever a rat spends time in the bright side, it's poked on the right non-Parkinsonian-affected paw. And so within a test session, rats associate the dark side with pain and nociception. And they associate the bright side with no nociception. And because rats are naturally, because they naturally prefer dark environments over bright environments, any time spent in the bright side represents active escape of witness behavior. And this test was done twice. Once before treatment and once after receiving treatment. And so the PD motor symptoms, as mentioned before, were confirmed with LAT testing. And however, three of our rats, their LAT tests could not be scored. So they also underwent step tests to assess for motor symptoms. And they also underwent tyrosine hydroxylase staining to assess for sufficient tyrosine hydroxylase depletion. And our results show that after the 6-hydroxydopamine lesion, the rats had a sufficient average tyrosine hydroxylase depletion of 80% in the right lesion side in the striatum and substantia nigra pars compacta. So then their pain, their neuropathy was confirmed with mechanical threshold tests through the von Frey filament testing. And the three stars representing a P value of less than 0.001 show that the rats that were Parkinsonian that had received the lesion had significantly more neuropathy than baseline rats. Proper electrode placement was confirmed with creosylviolet staining. The blue dots with the red outlines represent electrode placements that were confirmed with the rat brain atlas. And this red arrow represents an electrode placement as shown, as represented by a creosylviolet stain. And the green dot represents the, how it would be represented in the rat brain atlas showing that it was indeed placed in the STN. For each rat, we calculated the amount of bright time that they spent in the, the amount of time that they spent in the bright side during their first PAP before treatment. And we also calculated the amount of time spent in the bright side during their second PAP after treatment. We then calculated the percent change of time spent in the bright side between these two PAP tests. And what we found was that STN-DBS duloxetine, it decreased time spent in the bright side by an average of 33%. And the asterisk showing, representing a P value of less than 0.05 shows that STN-DBS duloxetine reduces escape avoidance behavior significantly more than duloxetine alone. Now, our results show that STN-DBS alone seem to increase escape avoidance behavior and time spent in the bright side, which is in the direction opposite of what is expected. And overall, duloxetine seems to have a minimal effect but with some great variability. And I would like to mention that increasing sample size to increase power is, of course, ongoing. So in conclusion, this shows that STN-DBS duloxetine could be a potential new therapy for PD pain because as Brian presented, previous studies showed that STN-DBS duloxetine has antinosusceptive effects. And this study shows that STN-DBS duloxetine reduces pain-related escape avoidance behavior as well. So this poses the question of what are the mechanisms behind STN-DBS and STN-DBS duloxetine? Escape avoidance behavior measured with the PIAP has been shown to correlate with neuronal activity in the anterior cingulate cortex of the descending inhibitory pain pathway. So this then creates the question of could the anterior cingulate cortex or the descending inhibitory pain pathway be a target for future PD pain therapies? Here are my references. And with that, I would like to thank all of our colleagues at the Department of Neuroscience and Experimental Therapeutics. And thank you for having me. Thank you.

STN-DBS

duloxetine

pain relief

Parkinson's disease

PD patients