α2δ-1–Bound N-Methyl-d-aspartate Receptors Mediate Morphine-induced Hyperalgesia and Analgesic Tolerance by Potentiating Glutamatergic Input in Rodents

Abstract

Background: Chronic use of μ-opioid receptor agonists paradoxically causes both hyperalgesia and the loss of analgesic efficacy. Opioid treatment increases presynaptic N-methyl-d-aspartate receptor activity to potentiate nociceptive input to spinal dorsal horn neurons. However, the mechanism responsible for this opioid-induced activation of presynaptic N-methyl-d-aspartate receptors remains unclear. α2δ-1, formerly known as a calcium channel subunit, interacts with N-methyl-d-aspartate receptors and is primarily expressed at presynaptic terminals. This study tested the hypothesis that α2δ-1-bound N-methyl-d-aspartate receptors contribute to presynaptic N-methyl-d-aspartate receptor hyperactivity associated with opioid-induced hyperalgesia and analgesic tolerance.Methods: Rats (5 mg/kg) and wild-type and α2δ-1-knockout mice (10 mg/kg) were treated intraperitoneally with morphine twice/day for 8 consecutive days, and nociceptive thresholds were examined. Presynaptic N-methyl-d-aspartate receptor activity was recorded in spinal cord slices. Coimmunoprecipitation was performed to examine protein-protein interactions.Results: Chronic morphine treatment in rats increased α2δ-1 protein amounts in the dorsal root ganglion and spinal cord. Chronic morphine exposure also increased the physical interaction between α2δ-1 and N-methyl-d-aspartate receptors by 1.5 ± 0.3 fold (means ± SD, P = 0.009, n = 6) and the prevalence of α2δ-1-bound N-methyl-d-aspartate receptors at spinal cord synapses. Inhibiting α2δ-1 with gabapentin or genetic knockout of α2δ-1 abolished the increase in presynaptic N-methyl-d-aspartate receptor activity in the spinal dorsal horn induced by morphine treatment. Furthermore, uncoupling the α2δ-1-Nmethyl-d-aspartate receptor interaction with an α2δ-1 C terminus-interfering peptide fully reversed morphine-induced tonic activation of N-methyl-d-aspartate receptors at the central terminal of primary afferents. Finally, intraperitoneal injection of gabapentin or intrathecal injection of an α2δ-1 C terminus-interfering peptide or α2δ-1 genetic knockout abolished the mechanical and thermal hyperalgesia induced by chronic morphine exposure and largely preserved morphine's analgesic effect during 8 days of morphine treatment.conclusions: α2δ-1-Bound N-methyl-d-aspartate receptors contribute to opioid-induced hyperalgesia and tolerance by augmenting presynaptic N-methyl-d-aspartate receptor expression and activity at the spinal cord level. What We Already Know about This Topic• Presynaptic N-methyl-d-aspartate receptors contribute to opioid tolerance and hyperalgesia as well as neuropathic pain • The α2δ-1 protein subunit enhances presynaptic N-methyl-daspartate receptor activity What This Article Tells Us That Is New• Using mouse and rat models, it was demonstrated that α2δ-1 is essential for the increase in presynaptic N-methyl-d-aspartate receptor activity seen during chronic morphine exposure • Inhibiting α2δ-1 activity using gabapentin or genetically deleting the gene coding for α2δ-1 results in diminished o...

Analgesia with Gabapentin and Pregabalin May Involve N-Methyl-d-Aspartate Receptors, Neurexins, and Thrombospondins

“…Such mEPSCs recorded in dorsal spinal cord (or trigeminal nucleus) neurons typically have rates in the range of 0.2 to 1.0 Hz, and the rate is augmented in response to experimental peripheral nerve damage (Li et al, 2014a;Li et al, 2014b;Zhou and Luo, 2015;Alles et al, 2017;Chen et al, 2018), chemotherapy-induced allodynia (Chen et al, 2019) allodynia from tolerance to repeated morphine treatment (Deng et al, 2019) or from artificial excess expression of α2δ-1 genes (Zhou and Luo, 2014). In each of these studies, the drugs gabapentin or pregabalin normalize pathologically elevated rates of mEPSCs in rat or mouse neuronal tissue with synapses in spinal cord dorsal horn (Patel et al, 2000;Li et al, 2014b;Matsuzawa et al, 2014;Zhou and Luo, 2014;Zhou and Luo, 2015;Park et al, 2016;Alles et al, 2017;Chen et al, 2018;Chen et al, 2019;Deng et al, 2019).…”

“…Such mEPSCs recorded in dorsal spinal cord (or trigeminal nucleus) neurons typically have rates in the range of 0.2 to 1.0 Hz, and the rate is augmented in response to experimental peripheral nerve damage (Li et al, 2014a;Li et al, 2014b;Zhou and Luo, 2015;Alles et al, 2017;Chen et al, 2018), chemotherapy-induced allodynia (Chen et al, 2019) allodynia from tolerance to repeated morphine treatment (Deng et al, 2019) or from artificial excess expression of α2δ-1 genes (Zhou and Luo, 2014). In each of these studies, the drugs gabapentin or pregabalin normalize pathologically elevated rates of mEPSCs in rat or mouse neuronal tissue with synapses in spinal cord dorsal horn (Patel et al, 2000;Li et al, 2014b;Matsuzawa et al, 2014;Zhou and Luo, 2014;Zhou and Luo, 2015;Park et al, 2016;Alles et al, 2017;Chen et al, 2018;Chen et al, 2019;Deng et al, 2019). Gabapentinoids reduced the rate of mEPSCs between glutamatergic neurons in rat entorhinal cortex (Cunningham et al, 2004), in neocortex neurons after cortical freeze lesions (Andresen et al, 2014;Lau et al, 2017), between neocortex and striatal neurons (Zhou et al, 2018), at glutamate neurons in hypothalamus of spontaneously hypertensive rats (Ma et al, 2018), at the mouse calyx of Held (Di Guilmi et al, 2011) and in cortico-striatal synapses after prolonged prior stimulation of striatum (Nagai et al, 2019).…”

“…In cases where it was tested, the ability of gabapentin and pregabalin to reduce spontaneous vesicle release in chronic pain models was absent if NMDA receptors were blocked in spinal cord dorsal horn neurons (Chen et al, 2018;Chen et al, 2019;Deng et al, 2019). Similarly, pregabalin reduced spontaneous vesicle release (measured by release of fluorescent dye from synaptic vesicles) from synapses in cultured hippocampal neurons (Micheva et al, 2006), but not with NMDA receptors blocked.…”

“…Similarly, pregabalin reduced spontaneous vesicle release (measured by release of fluorescent dye from synaptic vesicles) from synapses in cultured hippocampal neurons (Micheva et al, 2006), but not with NMDA receptors blocked. Since 2-1 is expressed mostly presynaptically, it is likely that presynaptic membranes are an important anatomical site of 2-1 interactions with NMDA receptors as suggested experimentally (Chen et al, 2018;Zhou et al, 2018;Chen et al, 2019;Deng et al, 2019). However, it will require additional studies to conclusively show that presynaptic NMDA receptors are uniquely sensitive to gabapentinoids.…”

“…F. LRP1 (lipoprotein related protein receptor 1, blue) binds to the 2-1 VWA domain via two extracellular ligand binding domains (Kadurin et al, 2017). Gabapentin interferes with the action of presynaptic NMDA receptors in several systems (Chen et al, 2018;Luo et al, 2018;Ma et al, 2018;Zhou et al, 2018;Chen et al, 2019;Deng et al, 2019) to reduce the spontaneous release of synaptic vesicles and decrease NMDA receptor function. C. Gabapentin interferes with the action of thrombospondin from astrocytes and this reduces presynaptic vesicle release and also reduces postsynaptic spine enlargement (Risher et al, 2018;Wang et al, 2020).…”