Journal Article

5-HT modulation of pain perception in humans

Silverdale, Monty A., Jones, Anthony K. P., Boyle, Yvonne, Power, Andrea, Anderson, Ian M., Martin, Sarah L.

2017

Overview

Introduction Although there is clear evidence for the serotonergic regulation of descending control of pain in animals, little direct evidence exists in humans. The majority of our knowledge comes from the use of serotonin (5-HT)-modulating antidepressants as analgesics in the clinical management of chronic pain. Objectives Here, we have used an acute tryptophan depletion (ATD) to manipulate 5-HT function and examine its effects of ATD on heat pain threshold and tolerance, attentional manipulation of nociceptive processing and mood in human volunteers. Methods Fifteen healthy participants received both ATD and balanced amino acid (BAL) drinks on two separate sessions in a double-blind cross-over design. Pain threshold and tolerance were determined 4 h post-drink via a heat thermode. Additional attention, distraction and temperature discrimination paradigms were completed using a laser-induced heat pain stimulus. Mood was assessed prior and throughout each session. Results Our investigation reported that the ATD lowered plasma TRP levels by 65.05 ± 7.29% and significantly reduced pain threshold and tolerance in response to the heat thermode. There was a direct correlation between the reduction in total plasma TRP levels and reduction in thermode temperature. In contrast, ATD showed no effect on laser-induced pain nor significant impact of the distraction-induced analgesia on pain perception but did reduce performance of the painful temperature discrimination task. Importantly, all findings were independent of any effects of ATD on mood. Conclusion As far as we are aware, it is the first demonstration of 5-HT effects on pain perception which are not confounded by mood changes.

• Publisher: Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: Adult / Affect - drug effects / Affect - physiology / Amino acids / Analgesia / Analgesics / Antidepressants / Attention - drug effects / Attention - physiology / Beverages / Biomedical and Life Sciences / Biomedicine / Care and treatment / Chronic pain / Clinical trials / Cross-Over Studies / Double-Blind Method / Emotions / Female / Health aspects / Heat / Humans / Male / Methods / Neuropsychology / Neurosciences / Original Investigation / Pain management / Pain Measurement - drug effects / Pain Measurement - methods / Pain perception / Pain Perception - drug effects / Pain Perception - physiology / Pharmacology/Toxicology / Psychiatry / Serotonin / Serotonin - blood / Temperature effects / Temperature perception / Tryptophan / Tryptophan - blood / Tryptophan - deficiency