The
ionotropic glutamate receptor subunit, GluK1 (GluR5), is expressed in many regions of the nervous system related to sensory transmission. Recently, a selective
ligand for the GluK1 receptor,
MSVIII-19 (8,9-dideoxy-neodysiherbaine), was synthesized as a derivative of
dysiherbaine, a toxin isolated from the marine sponge Lendenfeldia chondrodes.
MSVIII-19 potently desensitizes GluK1 receptors without channel activation, rendering it useful as a functional antagonist. Given the high selectivity for GluK1 and the proposed role for this
glutamate receptor in nociception, we sought to test the
analgesic potential of
MSVIII-19 in a series of models of inflammatory, neuropathic, and
visceral pain in mice.
MSVIII-19 delivered intrathecally dose-dependently reduced
formalin-induced spontaneous behaviors and reduced thermal
hypersensitivity 3 hours after
formalin injection and 24 hours after complete
Freund's adjuvant-induced
inflammation, but had no effect on mechanical sensitivity in the same models. Intrathecal
MSVIII-19 significantly reduced both
thermal hyperalgesia and mechanical
hypersensitivity in the chronic constriction injury model of
neuropathic pain, but had no effect in the
acetic acid model of
visceral pain. Peripheral administration of
MSVIII-19 had no
analgesic efficacy in any of these models. Finally, intrathecal
MSVIII-19 did not alter responses in Tail-flick tests or performance on the accelerating RotaRod. These data suggest that spinal administration of
MSVIII-19 reverses
hypersensitivity in several models of
pain in mice, supporting the clinical potential of GluK1 antagonists for the management of
pain.