Spinal γ-Aminobutyric Acid Interneuron Plasticity Is Involved in the Reduced Analgesic Effects of Morphine on Neuropathic Pain
Year: 2021
Type: article
Abstract: Systemic administration of morphine increases serotonin (5-HT) in the spinal dorsal horn (SDH), which attenuates the analgesic effects of morphine on neuropathic pain through spinal 5-HT3 receptors. We hypothesized that dysfunction of the descending serotonergic system, including the periaqueductal gray (PAG), contributes to attenuate the efficacy of morphine on neuropathic pain through spinal 5-HT3 receptors and GABA neurons. Morphine (100 ng) injected into the PAG produced analgesic effects in normal rats, but not in spinal nerve ligation (SNL) rats. In vivo microdialysis showed that PAG morphine increased the SDH 5-HT concentration in both groups. Intrathecal injection of the 5-HT3 receptor antagonist ondansetron and the GABA A receptor antagonist bicuculline attenuated the analgesic effects of PAG morphine in normal rats, but increased the effects in SNL rats. The increased analgesic effect of PAG morphine induced by bicuculline was reversed by pretreatment with the tropomyosin receptor kinase B (TrkB) antagonist K252a. Activation of spinal 5-HT3 receptors by 2-methyl-5-HT increased the GABA concentration in both groups. Morphine activates GABAergic interneurons in the SDH by activating descending serotonergic neurons. Functional changes in GABA A receptors from inhibitory to facilitatory through the activation of TrkB receptors may contribute to the attenuated efficacy of morphine against neuropathic pain. Perspective Although morphine provides strong analgesia against acute pain, it has limited efficacy against neuropathic pain. This article demonstrates that functional changes in GABA A receptors in the spinal dorsal horn after nerve injury might strongly contribute to the attenuation of opioid-induced analgesia for neuropathic pain.
Source: Journal of Pain
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $3,500
Awards: G1980904739, The role of the descending inhibitory system in endogenous analgesia, Elucidation of the Mechanism of Combination Effects of Neuropathic Pain Therapeutics: Toward Enhancing the Effects of Gabapentinoids, Research on the analgesic mechanisms and plasticity of the mesolimbic dopamine system, Identification of changes in spinal GABA receptor function and mechanisms of opioid effect attenuation in neuropathic pain., Development of Multimodel Pain Treatment using Nanotechnology & Power Assist, G4231250311, G7179218052
OpenAlex ID: W3206469730