The transient potential vanilloid 1 receptor (TRPV1) is a
calcium-permeable channel responsible for the transduction and modulation of acute and
chronic pain signaling. As such, this receptor is a potential target for the treatment of a number of
pain disorders. However,
AMG517, a TRPV1 antagonist, presents several clinical limitations that include the induction of severe
hyperthermia. The aim of this study was to investigate the possible interaction of the
flavonoid eriodictyol with the
TRPV1 receptor and to determine its putative antinociceptive and hyperthermic effects.
Eriodictyol was able to displace [(3)H]-
resiniferatoxin binding (IC(50)=47; 21-119nM) and to inhibit
calcium influx mediated by
capsaicin (IC(50)=44; 16-125nM), suggesting that
eriodictyol acts as a TRPV1 antagonist. Moreover,
eriodictyol induced antinociception in the intraplantar
capsaicin test, with maximal inhibition of 49±10 and 64±4% for oral (ID(50)=2.3; 1.1-5.7mg/kg) and intrathecal (ID(50)=2.2; 1.7-2.9nmol/site) administration, respectively.
Eriodictyol did not induce any change in body temperature or locomotor activity. Orally administered
eriodictyol (4.5mg/kg) prevented the nociception induced by
intrathecal injections of
capsaicin, as well as the non-
protein thiol loss and
3-nitrotyrosine (3-NT) formation induced by
capsaicin in spinal cord.
Eriodictyol also reduced the
thermal hyperalgesia and
mechanical allodynia elicited by complete
Freund's adjuvant (CFA) paw injection. In conclusion,
eriodictyol acts as an antagonist of the
TRPV1 receptor and as an
antioxidant; it induces antinociception without some of the side effects and limitations such as
hyperthermia that are expected for TRPV1 antagonists.