Abstract DP398: Just twenty minutes of intense exercise significantly impacts cortical GABA levels in chronic stroke individuals

Background: Previous studies show reduced gamma-aminobutyric acid (GABA) levels in the lesioned hemisphere of chronic stroke patients, linked to poorer motor learning and impaired cortical plasticity. In healthy models, exercise increases GABA levels. This imaging study aims to evaluate the impact of a single session of high-intensity interval training (HIIT) on GABA levels in chronic stroke participants, hypothesizing that factors like hemisphere, age, pre-exercise GABA levels, blood lactate changes, and timing since peak lactate influence this effect. Methods: Participants (ages 31-78, 2 females and 5 males) underwent MRI scans before and after a 20-minute HIIT routine, during which heart rate and blood lactate levels were measured. Magnetic resonance spectroscopy was performed on the motor cortex to determine water-normalized GABA concentrations. ANOVA in JMP Pro 16 was used to analyze post-HIIT GABA levels based on pre-HIIT GABA, hemisphere of collection (contra or ipsi), age, change in blood lactate, and time since peak blood lactate. Results: The analysis of post-HIIT GABA levels showed significant findings (F(5,8)=17.7, p=0.0004). Post-HIIT GABA levels were trending higher in the contra-lesional hemisphere compared to the ipsi-lesional hemisphere (t=1.92, p=0.09) and were significantly elevated when participants produced more blood lactate during exercise (t=4.42, p=0.002). Additionally, there was a significant negative correlation with age (t=-4.04, p=0.004). A noted trend indicated that GABA levels were higher 40 minutes post-HIIT compared to 20 minutes post-HIIT (t=1.79, p=0.11), suggesting that GABA metabolism remains elevated in the brain even after peripheral physiology has returned to baseline. Conclusions: Our study shows that GABA levels increase in both hemispheres after just 20 minutes of aerobic exercise. This finding suggests that rehabilitation strategies utilizing learning mechanisms post-stroke could benefit from improvements in the GABAergic system. Additionally, the effectiveness of exercise is linked to muscle effort, shown by the positive correlation between blood lactate and GABA levels. It's also essential to tailor exercise and rehabilitation plans based on the participant's age due to metabolic changes. Future research should investigate how long GABA metabolism remains elevated after exercise to improve treatment planning and effectiveness.