Docosahexaenoyl Serotonin is a potent TRPV1 antagonist [1].

The transient receptor potential vanilloid-type 1 (TRPV1) channel is a nonselective cation channel that may be activated by a variety of exogenous and endogenous physical and chemical stimuli. TRPV1 is decreased in the injured nerve fibers but increased in those proximal to the site damage. TRPV1 is a potential new target for the development of analgesic and anti-inflammatory drugs [1].

Docosahexaenoyl Serotonin is a hybrid molecule patterned after arachidonoyl serotonin. Arachidonoyl serotonin is a dual antagonist of TRPV1 and fatty acid amide hydrolase (FAAH) with IC50 values of 0.27 and 8 μM, respectively. Arachidonoyl serotonin was highly effective against both acute and chronic peripheral pain [1][2]. The effects of replacing the arachidonoyl portion with docosahexaenoyl had not been studied [1].

References:
[1].  Ortar G, Cascio MG, De Petrocellis L, et al. New N-arachidonoylserotonin analogues with potential "dual" mechanism of action against pain. J Med Chem. 2007 Dec 27;50(26):6554-69.
[2].  Maione S, De Petrocellis L, de Novellis V, et al. Analgesic actions of N-arachidonoyl-serotonin, a fatty acid amide hydrolase inhibitor with antagonistic activity at vanilloid TRPV1 receptors. Br J Pharmacol. 2007 Mar;150(6):766-81.