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Published on: July 16, 2014
Descending serotonergic facilitation of spinal ERK activation and pain behavior
Camilla I Svensson1, Thao K Tran, Bethany Fitzsimmons
1Department of Anesthesiology, University of California - San Diego, 9500 Gilman drive, La Jolla, CA 92093-0818, USA.
Abstract:
Serotonin (5-HT) derived from bulbo-spinal projection is released by nociceptive input into the spinal dorsal horn. Here we report that formalin injection in the paw produced pain behavior (flinching) and phosphorylation of spinal ERK1/2 (P-ERK1/2, indicating activation) in rats. Depletion of spinal 5-HT by intrathecal (IT) 5,7-DHT, a serotonergic neurotoxin, profoundly reduced formalin evoked flinching and the increase in P-ERK1/2. Ondansetron (a 5-HT3 receptor antagonist) at IT doses that inhibited flinching also attenuated spinal ERK activation. These findings reveal that primary afferent-evoked activation of spinal ERK requires the input from an excitatory 5-HT descending pathway.
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