Physical Exercise Affects Serotoninergic System in Horse Leukocytes
Authors: Bruschetta Giuseppe, D’Ascola Angela, Medica Pietro, Ferlazzo Alida Maria
Journal: Journal of Equine Veterinary Science
Summary
# Editorial Summary Serotonin plays a multifaceted role in equine physiology beyond mood regulation, with emerging evidence suggesting involvement in immune and metabolic function at the cellular level. Bruschetta and colleagues investigated how an intensive training session alters the serotoninergic signalling pathway in 12 trained racehorses, measuring plasma serotonin concentrations and gene expression of serotonin transporters and receptors in peripheral blood mononuclear cells (PBMC) at baseline, 30 minutes post-exercise, and 2 hours post-exercise. The acute exercise response involved significantly elevated circulating serotonin and increased expression of the 5HT1A and 5-HT2A receptors in leukocytes at 30 minutes, coupled with decreased serotonin transporter (SERT) expression and reduced pro-inflammatory cytokine markers (IL-1β and TNF-α). This pattern suggests that intensive training triggers a transient shift in how leukocytes handle serotonin—reduced cellular uptake via SERT appears to elevate plasma concentrations whilst simultaneously modulating immune signalling. For equine practitioners, these findings indicate that training stress induces measurable neuroendocrinological changes that may influence recovery, immune competence, and training tolerance, potentially informing periodisation strategies and markers for overtraining in competition horses.
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Practical Takeaways
- •Understanding serotonin dynamics during intense training may help optimize recovery protocols and manage stress responses in racing horses
- •The transient changes in leukocyte gene expression suggest exercise induces measurable neuroendocrine adaptations that could be monitored to assess training load and recovery adequacy
- •Anti-inflammatory effects observed post-training support the physiological benefits of structured exercise, though the transient nature suggests timing of recovery management is important
Key Findings
- •Intensive training significantly increased plasma serotonin (5-HT) levels at 30 minutes post-exercise compared to baseline
- •Serotonin transporter (SERT) expression in leukocytes was significantly decreased at 30 minutes post-training, suggesting reduced 5-HT reuptake capacity
- •5-HT1A and 5-HT2A receptor mRNA expression increased post-exercise while 5-HT1B and 5-HT7 receptor expression decreased, indicating exercise-induced shifts in receptor sensitivity
- •Inflammatory cytokine mRNAs (IL-1β and TNF-α) were significantly decreased in leukocytes 30 minutes post-training, suggesting transient anti-inflammatory effects