Serotonin and experimental pain in healthy young volunteers

Objective: The role of serotonin in the modulation of nociceptive input has been widely studied, and a link between serum serotonin (S-5HT) and pain thresholds elicited in patients with chronic painful pathologies has been shown. In the light of contradictory concepts on pain message modulation by S-5HT, this study tries to define whether S-5HT displays a nociceptive or antinociceptive role in experimental pain evaluation in healthy volunteers. Design: In 20 healthy young volunteers, 10 men and 10 women (21 +/- 2 years old), blood serotonin measurements were made, pressure pain thresholds was determined, and statistical analysis was performed. Results: This study showed a significant negative correlation of total blood serotonin with experimental pain detection threshold (P < 0.05, r = 0.444), but not with pain tolerance, while sex-related correlations of serotonin and thresholds were not significant. Lower serotonin concentration (P = 0.02), higher pain threshold (P < 0.01), and higher pain tolerance (P = 0.02) in men than in women were observed. Conclusion: Low pain detection thresholds may be explained by a peripheral nociceptive effect of serotonin. Pain tolerance does not, however, encompass a similar pattern of serotoninergic involvement in pain control and may include other components that remain to be elucidated. These results call for further studies on a larger population.