Extracellular Levels of 5HT and 5HIAA Increase after an Inflammatory Process in the Rat’s Insular Cortex

Abstract

Serotonin (5HT) in the central nervous system has been associated with pain processing and modulation. The insular cortex (IC) plays an important role in the development and perception of the inflammatory and chronic pain. The role of the serotoninergic system in IC has not been completely studied. We used micro-dialysis in freely moving rats to determine the extracellular release of 5HT and its main metabolite (5HIAA) in the IC during an inflammatory process. Results showed an increase of extracellular levels of 5HT and 5HIAA in the IC during carrageenan-induced inflammation and this augmentation correlates with a decrease of behavioral mechanonociceptive response. Furthermore, the exogenous administration of 5HT and 5HIAA in the IC increases the nociceptive response. Our current data imply that the serotoninergic system in the IC participates in the long-term pain process.