Chronic opioid potentiates presynaptic but impairs postsynaptic N-methyl-D-aspartic acid receptor activity in spinal cords: implications for opioid hyperalgesia and tolerance.

ABSTRACT: Opioids are the most effective analgesics for the treatment of moderate to severe pain. However, chronic opioid treatment can cause both hyperalgesia and analgesic tolerance, which limit their clinical efficacy. In this study, we determined the role of pre- and postsynaptic NMDA receptors (NMDARs) in controlling increased glutamatergic input in the spinal cord induced by chronic systemic morphine administration. Whole-cell voltage clamp recordings of excitatory postsynaptic currents (EPSCs) were performed on dorsal horn neurons in rat spinal cord slices. Chronic morphine significantly increased the amplitude of monosynaptic EPSCs evoked from the dorsal root and the frequency of spontaneous EPSCs, and these changes were largely attenuated by blocking NMDARs and by inhibiting PKC, but not PK

SUBMITTER: Zhao YL 

PROVIDER: S-EPMC3408179 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature