Background: Despite the extensive number of studies performed in the last 50 years,
aimed at describing the role of serotonin and its receptors in pain modulation at the spinal cord
level, several aspects are still not entirely understood. The interpretation of these results is often
complicated by the use of different pain models and animal species, together with the lack of highly
selective agonists and antagonists binding to serotonin receptors.
Method: In this review, a search has been conducted on studies investigating the modulatory action
exerted by serotonin on specific neurons and circuits in the spinal cord dorsal horn. Particular attention
has been paid to studies employing electrophysiological techniques, both in vivo and in vitro.
Conclusion: The effects of serotonin on pain transmission in dorsal horn depend on several factors,
including the type of receptors activated and the populations of neurons involved. Recently, studies
performed by activating and/or recording from identified neurons have importantly contributed to
the understanding of serotonergic modulation on dorsal horn circuits.