Spinal metabotropic glutamate receptor 4 is involved in neuropathic pain.

Glutamate receptors (GluRs) play a critical role in pain pathway. Recent studies have shown that activation of spinal group III metabotropic GluRs attenuated hyperalgesia in neuropathic pain model rats. However, it is unclear which subtype of group III metabotropic GluRs is involved in neuropathic pain. In this study, we have shown that spinal administration of metabotropic GluRs (mGluR4)-positive allosteric modulator (VU0155041) dose dependently attenuated hyperalgesia in neuropathic pain model rats, whereas that of mGluR7-positive allosteric modulator (AMN082) did not. Furthermore, we confirmed that it was mGluR4 not mGluR7, whose expression was downregulated in the spinal dorsal horn after spinal nerve ligation. Thus, these results suggest the alteration of the spinal mGluR4 expression that contributes to the development of neuropathic pain.