Physical Exercise Affects Serotoninergic System in Horse Leukocytes.

This research explores how intensive training in racehorses impacts serotonin levels in the body and related functions, particularly in leukocytes. The study indicates that physical training may reduce serotonin storage and increase plasma serotonin concentrations, potentially impacting the performance and physiological response of racehorses to exercise.

Details of the Study

• The goal of this research was to understand the impact of an intense training session on the serotonin system in horse leukocytes. The subjects of the study were 12 trained horses regularly involved in daily training.
• Researchers were particularly interested in changes to plasma serotonin levels, the expression of serotonin transporter (SERT), serotonin receptors, and inflammation-related proteins such as interleukin-1 beta and tumor necrosis factor-alpha.
• Measurements were taken at three different points — before the training session (T0), 30 minutes after the session (T1) and two hours post-training (T2).

Methods and Analysis

• The researchers used an enzyme-linked immunosorbent assay to analyze changes in plasma serotonin levels in a platelet-poor plasma fraction across the three time points.
• To examine the changes on a cellular level, they isolated peripheral blood mononuclear cells (PBMCs) and then used real-time polymerase chain reaction to measure mRNA levels of SERT, serotonin receptors, and cytokines.

Results and Interpretation

• Post-training (T1), horses showed higher levels of plasma serotonin and reduced levels of serotonin transporter and serotonin receptors. This suggests that physical exercise reduced the storage of serotonin, leading to increased plasma serotonin concentrations.
• Both interleukin-1 beta and tumor necrosis factor-alpha levels dropped in PBMCs at T1, indicating that post-training, the expression of these cytokines was reduced.
• Overall, the changes seem to illustrate that exercise triggers a short-term neuroendocrinological response in the horses. The authors suggest that a deeper understanding of these impacts could help optimize training protocols for racehorses in the future.