Pain Processing: 

How Quercetin Impacts Pain Processing

Quercetin is a naturally occurring flavonoid found in fruits, vegetables, and medicinal plants, including onions, apples, berries, capers, and green tea.[1][2] As one of the most extensively studied dietary flavonoids, quercetin has demonstrated a broad spectrum of pharmacological activity relevant to the experience of pain due its potent anti-inflammatory, antioxidant, and neuroprotective properties.[1][2][3]

 

See:

  1. Quercetin
  2. Quercetin for Chronic Pain: A Patient Guide

 

     How Nutraceuticals Impact Pain Processing

  1. How Acetyl-L-Carnitine (ALC) Impacts Pain Processing
  2. How Alpha-Lipoic Acid (ALA) impacts pain processing
  3. How Boswellia Impacts Pain Processing
  4. How CoQ10 Impacts Pain Processing
  5. How Curcumin Impacts Pain Processing
  6. How Magnesium Impacts Pain Processing
  7. How Melatonin Impacts Pain Processing
  8. How Omega-3 fatty acids (EPA and DHA) Impact Pain Processing
  9. How N-Acetyl Cysteine (NAC) Impacts Pain Processing
  10. How Nicotinamide Riboside (NR) Impacts Pain Processing
  11. How PEA (Palmitoylethanolamide) Impacts Pain Processing
  12. How Quercetin Impacts Pain Processing
  13. How Resveratrol Impacts Pain Processing
  14. How Sulforaphane (SFN): Impacts Pain Processing
  15. How Taurine Impacts Pain Processing

 

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Definitions and Terms Related to Pain

 

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How Quercetin Impacts Pain Processing

Introduction

Quercetin has demonstrated a broad spectrum of pharmacological actions relevant to the process of sending pain signals from an area of injury to the brain, resulting in the experience of pain. Quercetin impacts the processing of pain signaling based on its different properties, including potent anti-inflammatory, antioxidant, and neuroprotective properties.[1][2][3]

   Pain Processing involves complex nerve interactions that:

  1. Starts with the detection of damaged tissues by specialized pain receptors,
  2. Followed by sending pain signals to the spinal cord through peripheral nerves, then
  3. Processing of the signals in the spinal cord, then
  4. Forwarding the signals up ascending pain pathways to various parts of the brain, then
  5. Processing of the pain signals in the brain (supraspinal integration)
  6. Followed, finally, by the brain sending pain signals back down descending pain pathways in the spinal cord to impact the pain signal processing in the spinal cord (descending pain modulation).

At each of these stages, or levels, of pain processing, the pain signaling can be modified referred to as pain modulation.  Pain modulation can result in the pain experience being magnified or suppressed, temporarily or in some cases permanently. There are many situations and processes that modulate the pain experience, but the focus here is limited to the magnification of pain that occurs in the pathologic processing of pain signals in nerves in the peripheral nervous system and/or the spinal cord and brain (the central nervous system).

This pathologic pain processing that results in heightened sensitivity and magnification of the pain experience, it is referred to as “Sensitization” which  can originate in the peripheral and/or the central nervous system, termed “Peripheral Sensitization” and “Central Sensitization.”

Central to the pathophysiology of pain processing leading to Peripheral Sensitization and Central Sensitization are 4 interconnected conditions, sometimes referred to as “the 4 Demons of Pain:”

  1. Systemic Inflammation
  2. Neuroinflammation
  3. Oxidative Stress
  4. Mitochondrial Dysfunction.[1][4][5]

Quercetin demonstrates mechanistic activity across all four of these domains, positioning it as a multi-target nutraceutical for pain management.[3][6]

Understanding the Four Demons

Systemic Inflammation, Neuroinlammation, Oxidative Stress and Mitochondrial Dysfunction are 4 pathological processes/conditions that contribute to chronic pain by creating a cycle of tissue damage, immune cell activation, and pain amplification. By disrupting normal cellular physiology, these conditions also contribute to the development and progression of chronic diseases, including diabetes, heart disease, stroke, chronic kidney and liver disease, rheumatoid arthritis, cancer and Alzheimer’s.

  1. Systemic inflammation (SI) is a widespread inflammatory response throughout the body, triggered by infection, injury, stress and other conditions. It involves activation of the immune system with the release of pro-inflammatory compounds that contribute to chronic pain and lead to other health issues. Symptoms of SI include increased pain, fatigue, cognitive problems, depression, decreased motivation for physical activity and, in severe cases, organ dysfunction. While inflammation is a natural part of the healing process, chronic or excessive SI contributes to the development of heart disease, diabetes, and autoimmune disorders like rheumatoid arthritis.
  2. Neuroinflammation (NI), a component of systemic inflammation, is inflammation within the central nervous system (brain and spinal cord). SI releases inflammatory compounds that cross into the brain and spinal cord that activate immune cells causing NI and contributes to the progression of acute to chronic pain. NI is characterized by activation of immune cells (glial cells and astrocytes) in the nervous system that release inflammatory chemicals like cytokines, proteases, and free radicals such as reactive oxygen (ROS), and nitrogen species (RNS). When these immune cells remain activated, neuroinflammation persists and drives chronic pain.
  3. Oxidative Stress (OS) is an imbalance of excessive “oxidants” (“oxidizing” or chemically active agents (including ROS and NOS) obtained from the diet or produced by the body coupled with insufficient “antioxidants,” the compounds that neutralize oxidants. Excessive oxidants damage nerve cells and other tissues causing and maintaining pain. Antioxidants are manufactured by the body, but sufficient dietary intake of antioxidants is critical for good health. OS and chronic SI co-exist and feed each other, damaging tissues in a vicious cycle that further worsens pain.
  4. Mitochondrial Dysfunction (MD). Mitochondria are organelles found in cells that function as the “power stations” of cells in that they process food into energy. In addition to providing energy, they play a major role in maintaining antioxidants to combat OS and SI. Because mitochondria impact the metabolism of all cells, they play a huge role in general health. Impairment of mitochondrial function (dysfunction) contributes to many conditions including chronic pain, obesity, migraines, fibromyalgia, diabetes, heart disease and neurodegenerative diseases like Alzheimers. In MD, energy production goes down and fatigue develops along with impaired physical functioning, even if more calories are ingested. MD is the hallmark of conditions such as obesity and fibromyalgia. Mitochondrial dysfunction leads to the metabolic impairment that is found in many chronic diseases including depression, bipolar disorders and premature aging.

The Impact of Quercetin in Pain Processing and the 4 Pathological Processes

   1. Systemic Inflammation:

         Quercetin exerts striking anti-inflammatory effects through multiple mechanisms:[1][7]

    1. NF-κB Pathway Inhibition: Quercetin significantly attenuates NF-κB activation by inhibiting IκBα phosphorylation and preventing nuclear translocation of p65-NF-κB, thereby reducing transcription of pro-inflammatory genes.[7][8][9]
    2. Cytokine Suppression: Quercetin dose-dependently reduces production and secretion of pro-inflammatory cytokines including TNF-α, IL-1β, IL-6, and IL-8 in both peripheral immune cells and neural tissues.[7][8][9][10]
    3. COX-2 and LOX Inhibition: Quercetin inhibits cyclooxygenase-2 (COX-2) and lipoxygenase (LOX) expression and activity, reducing prostaglandin and leukotriene synthesis.[1][11][12]
    4. Mast Cell Stabilization: Quercetin preserves mast cell integrity and inhibits histamine release, reducing inflammatory mediator cascades.[1][13]
    5. M1/M2 Macrophage Polarization: Quercetin shifts macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotype, reducing inflammatory cytokine production while enhancing IL-10 expression.[10][14]
    6. In a randomized controlled trial, 500 mg/day quercetin supplementation for 8 weeks significantly reduced plasma hs-TNFα levels and improved clinical symptoms in women with rheumatoid arthritis.[15]

    2  Neuroinflammation

Quercetin demonstrates potent anti-neuroinflammatory effects through modulation of microglial activation and astrocyte reactivity:[9][10][4][16]

    1. Microglial Modulation: Quercetin suppresses LPS-induced microglial activation, reducing secretion of IL-6 (by 96%), TNF-α (by 87%), and nitric oxide (by 42%) in BV-2 microglial cells. It inhibits iNOS expression and NF-κB activation through reduced IκBα phosphorylation.[9][17]
    2. NLRP3 Inflammasome Inhibition: Quercetin decreases NLRP3 inflammasome activation and pyroptosis-related proteins (active caspase-1, GSDMD N-terminus, cleaved IL-1β) in microglia, protecting neurons from inflammasome-mediated neurotoxicity.[16]
    3. M1/M2 Microglial Polarization: Quercetin promotes microglial phenotype shift from neurotoxic M1 to neuroprotective M2, reducing neuronal pyroptosis and ferroptosis.[10][14]
    4. Astrocyte Regulation: Quercetin inhibits reactive astrogliosis by reducing GFAP expression and suppressing astrocyte-mediated inflammatory signaling through TAK1, IKK, and JNK2 phosphorylation inhibition.[18][19][20]
    5. Nrf2/HO-1 Pathway Activation: Quercetin upregulates the Nrf2 antioxidant pathway and induces heme oxygenase-1 (HO-1) expression in microglial cells, providing cytoprotection against oxidative and inflammatory stress.[17][12]

   3. Oxidative Stress

Quercetin is recognized as one of the most potent dietary antioxidants, with multiple mechanisms for reducing oxidative stress:[1][7][2][21]

    1. Direct ROS Scavenging: The catechol B-ring and hydroxyl groups of quercetin enable direct scavenging of superoxide, hydroxyl radicals, and peroxynitrite.[1][2]
    2. NADPH Oxidase Inhibition: Quercetin suppresses NOX2-derived superoxide generation through HO-1-dependent mechanisms, reducing NADPH oxidase activity in macrophages and neural tissues.[8][22][21]
    3. Endogenous Antioxidant Enhancement: Quercetin dose-dependently increases activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), while enhancing expression of GCLC, GCLM, and NQO1 through AMPK and Akt signaling.[7][10]
    4. Nrf2 Pathway Activation: Quercetin promotes nuclear accumulation of Nrf2 and downregulation of Keap1, activating the antioxidant response element (ARE) and inducing phase II detoxification enzymes.[22][17][23]
    5. Inhibition of Oxidative Enzymes: Quercetin inhibits xanthine oxidase, monoamine oxidase-A, lipoxygenase, myeloperoxidase, and other ROS-generating enzymes.[21][24]

   4. Mitochondrial Dysfunction

      Quercetin demonstrates significant effects on mitochondrial function and biogenesis:[25][5][26][27]

    1. Mitochondrial Biogenesis: Quercetin stimulates expression of mitochondrial biogenesis regulators including SIRT1, PGC-1α, and TFAM, promoting mitochondrial DNA replication and respiratory complex synthesis.[25][26][23]
    2. Complex I Activity: Quercetin dose-dependently recovers mitochondrial complex I activity impaired by metabolic stress, improving electron transport chain function.[25]
    3. Membrane Potential Preservation: Quercetin counteracts detrimental increases in inner mitochondrial membrane proton leakage, maintaining mitochondrial membrane potential (ΔΨm).[25][5]
    4. NAD+/NADH Ratio: Quercetin increases cellular NAD+/NADH ratio within 2 hours of treatment, supporting mitochondrial oxidative metabolism and SIRT1 activation.[25]
    5. Mitophagy Promotion: Quercetin promotes mitophagy to enhance elimination of damaged mitochondria, reducing mtROS accumulation and subsequent NLRP3 inflammasome activation.[16]
    6. Redox Interaction with ETC: Quercetin interacts with the electron transport chain, modulating mitochondrial redox status and ATP generation, which may contribute to both its protective and hormetic effects.[5][27]

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SECTION 2: PAIN PROCESSING PATHWAY ANALYSIS (LEVELS 1-6)

   Level 1: Peripheral Nociception (Pain Receptor Transduction)

      Quercetin exerts significant effects at the level of peripheral nociceptors, modulating both transduction and sensitization processes:[3][13][11][28]

  • Ion Channel Modulation:
    1. TRPV1 Inhibition: Quercetin ameliorates paclitaxel-induced neuropathic pain by blocking PKCε-dependent activation of TRPV1 channels in dorsal root ganglia (DRG), reducing heat hyperalgesia. Quercetin inhibits capsaicin-induced nociception by 75.5%.[13][29]
    2. Voltage-Gated Sodium Channel Blockade: Quercetin blocks voltage-gated sodium (Nav) channels in trigeminal ganglion (TG) sensory neurons, reducing peak current density and neuronal excitability. Local administration of 1 mM quercetin demonstrates greater analgesic potency than 1% lidocaine (37 mM) in inflamed tissue.[30][31][28]
    3. Voltage-Gated Potassium Channel Activation: Quercetin opens voltage-gated K+ channels, hyperpolarizing nociceptive neurons and reducing action potential generation.[31]
    4. P2X Receptor Inhibition: Quercetin inhibits upregulated P2X4 receptor expression in DRG satellite glial cells, reducing ATP-activated currents and p38MAPK activation in diabetic neuropathic pain.[32]
  • Peripheral Sensitization Mechanisms:
    1. COX-2 Inhibition: Quercetin inhibits peripheral COX-2 expression and prostaglandin synthesis, reducing inflammatory sensitization of nociceptors.[11][12]
    2. Mast Cell Stabilization: Quercetin stabilizes mast cells and inhibits histamine release from paclitaxel-stimulated basophils, preventing histamine-mediated nociceptor sensitization.[13]
    3. Inflammatory Mediator Reduction: Quercetin reduces peripheral levels of TNF-α, IL-1β, IL-6, and other sensitizing inflammatory mediators.[18][12][15]
  • Functional Outcomes:
    1. Local quercetin injection suppresses excitability of nociceptive primary sensory TG neurons in response to both non-noxious and noxious mechanical stimulation.[28][31]
    2. Quercetin demonstrates local anesthetic effects comparable to or exceeding lidocaine, inhibiting both generator potentials and action potentials in nociceptive nerve terminals.[28]

—

   Level 2: Primary Afferent Transmission to Spinal Cord

      Quercetin modulates primary afferent neuron function and transmission from peripheral tissues to the spinal cord:[3][6][33][32]

  • Dorsal Root Ganglion (DRG) Effects:
    1. Neuronal Excitability: Quercetin reduces hyperexcitability of DRG neurons in inflammatory and neuropathic pain models by modulating voltage-gated ion channels and reducing inflammatory mediator expression.[13][32]
    2. P2X4 Receptor Modulation: In diabetic neuropathic pain, quercetin inhibits upregulated P2X4 receptor expression in DRG satellite glial cells (SGCs), reducing purinergic signaling and p38MAPK phosphorylation.[32]
    3. PKCε Translocation Inhibition: Quercetin inhibits PKCε translocation from cytoplasm to membrane in DRG neurons, reducing TRPV1 sensitization.[13]
    4. TNF-α-TNFR1 Signaling: Quercetin attenuates TNF-α-TNFR1-ERK1/2 signaling pathway activation in DRG, reducing inflammatory hyperalgesia.[18]
  • Satellite Glial Cell Modulation:
    1. Quercetin reduces satellite glial cell activation (decreased GFAP co-expression with P2X4) in DRG, attenuating neuron-glia inflammatory crosstalk.[32]
  • Afferent Fiber Function:
    1. By reducing peripheral sensitization and DRG neuronal hyperexcitability, quercetin decreases aberrant afferent signaling to the spinal cord dorsal horn.[3][6]

—

   Level 3: Spinal Cord Dorsal Horn Processing (First Synapse)

      Quercetin demonstrates significant effects on spinal cord dorsal horn processing, targeting central sensitization mechanisms:[33][18][12]

  • Synaptic Plasticity Modulation:
    1. mTOR/p70S6K Pathway Inhibition: Quercetin attenuates diabetic neuropathic pain by inhibiting mTOR/p70S6K pathway-mediated changes in synaptic morphology, reducing total dendritic length, dendritic branch number, and dendritic spine density in spinal dorsal horn neurons.[33]
    2. Synaptic Protein Regulation: Quercetin decreases upregulated expression of synaptic plasticity-associated proteins PSD-95 and synaptophysin in spinal dorsal horn, reducing maladaptive synaptic strengthening.[33]
  • Spinal Glial Cell Inhibition:
    1. Microglial Inhibition: Quercetin reduces spinal cord microglial activation, decreasing Iba-1 expression and microglial-derived inflammatory mediators.[12][18]
    2. Astrocyte Inhibition: Quercetin suppresses spinal astrocyte activation, reducing GFAP expression and astrocyte-mediated NF-κB signaling.[18][12]
    3. Glial Cytokine Reduction: Quercetin inhibits spinal cord production of TNF-α, IL-1β, and IL-6 from activated glial cells.[12]
  • Central Sensitization Mechanisms:
    1. c-Fos Reduction: Quercetin decreases c-Fos activity in dorsal horn neurons, indicating reduced nociceptive neuronal activation.[18]
    2. ROS-ERK1/2 Signaling: Quercetin modulates ROS-mediated ERK1/2 signaling in spinal cord, attenuating central sensitization.[18]
    3. Toll-Like Receptor Inhibition: Quercetin inhibits TLR signaling in spinal astrocytes by reducing TAK1, IKK, and JNK2 phosphorylation, decreasing NF-κB-mediated inflammatory gene transcription.[19]
  • Wide Dynamic Range (WDR) Neuron Effects:
    1. Systemic quercetin administration significantly decreases discharge frequency of spinal trigeminal nucleus caudalis (SpVc) WDR neurons in response to both non-noxious and noxious mechanical stimuli.[11]
    2. Quercetin reduces spontaneous discharge and restores expanded receptive field size in inflamed animals to control levels.[11]

—

   Level 4: Ascending Spinal Pathways and Supraspinal Processing

      Quercetin’s effects on ascending pain pathways and supraspinal structures are mediated through its anti-inflammatory, antioxidant, and neuroprotective mechanisms:[4][16][14][6]

  • Neuroinflammation in Supraspinal Structures:
    1. Quercetin suppresses neuroinflammation in brain regions involved in pain processing by inhibiting microglial activation and NLRP3 inflammasome signaling.[4][16]
    2. In models of neurodegeneration and neuroinflammation, quercetin reduces brain levels of pro-inflammatory cytokines and protects neurons from inflammatory neurotoxicity.[4][16][14]
  • Oxidative Stress Reduction:
    1. Quercetin reduces oxidative stress in brain tissue through Nrf2/HO-1 pathway activation and direct ROS scavenging, protecting supraspinal pain processing regions from oxidative damage.[4][26][23]
  • Mitochondrial Protection:
    1. Quercetin promotes mitochondrial biogenesis and function in neuronal cells, supporting energy metabolism in supraspinal pain processing centers.[25][5][26]
  • Neuroprotection:
    1. Quercetin protects neurons from NLRP3 inflammasome-mediated pyroptosis and ferroptosis, preserving neuronal integrity in pain-relevant brain regions.[16][14]
    2. By promoting mitophagy and reducing mtROS accumulation, quercetin prevents mitochondrial dysfunction-induced neuronal damage.[16]

—

   Level 5: Thalamic and Cortical Processing and Pain Perception

       Quercetin’s effects on higher-order pain processing involve modulation of neuroinflammation, oxidative stress, and neurotransmitter systems:[4][6][34][24]

  • Cortical Neuroinflammation:
    1. Quercetin attenuates neuroinflammation in cortical regions through NF-κB and NLRP3 inflammasome inhibition, potentially reducing inflammatory contributions to pain perception.[4][16]
  • Neurotransmitter Modulation:
    1. Serotonergic System: Quercetin modulates serotonin (5-HT) availability and signaling. It weakly inhibits monoamine oxidase-A (MAO-A) in brain mitochondria, potentially increasing 5-HT levels. Quercetin’s analgesic effects are partially reversed by serotonin antagonists (ketanserin, methysergide) and the serotonin synthesis inhibitor p-chlorophenylalanine.[24][29]
    2. GABAergic System: Quercetin interacts with GABA receptors, with evidence suggesting modulation of GABA(A) receptor function. Its analgesic action is reversed by both GABA(A) antagonist (bicuculline) and GABA(B) antagonist (baclofen).[29][35][36]
  • Affective Components of Pain:
    1. Quercetin demonstrates antidepressant-like effects through modulation of serotonergic neurotransmission and SERT (serotonin transporter) function, potentially influencing affective dimensions of pain.[34]
    2. Quercetin’s anxiolytic effects through GABA receptor interaction may modulate anxiety-related amplification of pain perception.[35]

—

   Level 6: Descending Pain Modulation

      Quercetin influences descending pain modulatory systems through multiple neurotransmitter pathways:[6][29][37]

  • Serotonergic Descending Modulation:
    1. Quercetin’s analgesic effects involve the serotonergic system, as demonstrated by reversal with serotonin antagonists and synthesis inhibitors.[29]
    2. In visceral pain models, quercetin attenuates 5-HT availability in the colon by reducing enterochromaffin cell density and tryptophan hydroxylase expression, modulating peripheral serotonergic signaling.[37]
    3. Quercetin inhibits MAO-A activity in brain mitochondria, potentially enhancing serotonergic tone in descending modulatory pathways.[24]
  • GABAergic Modulation:
    1. Quercetin’s antinociceptive effects are mediated in part through GABAergic mechanisms, with both GABA(A) and GABA(B) receptor involvement.[29]
    2. Quercetin demonstrates binding affinity for GABA receptor subunits (α5, β1, β2), suggesting direct modulation of inhibitory neurotransmission.[35][36]
  • Opioidergic System:
    1. Preclinical evidence suggests quercetin modulates the opioidergic system as part of its analgesic mechanism.[6]
  • Nitric Oxide Pathway:
    1. Quercetin’s antinociceptive action involves the L-arginine-nitric oxide pathway, as demonstrated in pharmacological antagonism studies.[29]
  • Integrated Descending Modulation:
    1. By modulating serotonergic, GABAergic, opioidergic, and nitric oxide systems, quercetin may enhance descending inhibitory control over spinal nociceptive processing.[6][29]

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  32. Quercetin Relieved Diabetic Neuropathic Pain by Inhibiting Upregulated P2X Receptor in Dorsal Root Ganglia. Yang R, Li L, Yuan H, et al. Journal of Cellular Physiology. 2019;234(3):2756-2764. doi:10.1002/jcp.27091.
  33. Quercetin Attenuates Diabetic Neuropathic Pain by Inhibiting mTOR/p70S6K Pathway-Mediated Changes of Synaptic Morphology and Synaptic Protein Levels in Spinal Dorsal Horn of Db/Db Mice. Wang R, Qiu Z, Wang G, et al. European Journal of Pharmacology. 2020;882:173266. doi:10.1016/j.ejphar.2020.173266.
  34. The Quercetin-Serotonin Transporter (SERT) Connection: A New Hope for Depression Therapy?. Murthy MK. Psychopharmacology. 2025;:10.1007/s00213-025-06889-6. doi:10.1007/s00213-025-06889-6.
  35. Anxiolytic-Like Effect of Quercetin Possibly Through GABA Receptor Interaction Pathway: In Vivo and in Silico Studies. Islam MS, Hossain R, Ahmed T, et al. Molecules (Basel, Switzerland). 2022;27(21):7149. doi:10.3390/molecules27217149.
  36. Flavonoid Modulation of Ionic Currents Mediated by GABA(A) and GABA(C) Receptors. Goutman JD, Waxemberg MD, Doñate-Oliver F, Pomata PE, Calvo DJ. European Journal of Pharmacology. 2003;461(2-3):79-87. doi:10.1016/s0014-2999(03)01309-8.
  37. Quercetin Attenuates Visceral Hypersensitivity and 5-Hydroxytryptamine Availability in Postinflammatory Irritable Bowel Syndrome Rats: Role of Enterochromaffin Cells in the Colon. Qin HY, Zang KH, Zuo X, Wu XA, Bian ZX. Journal of Medicinal Food. 2019;22(7):663-671. doi:10.1089/jmf.2018.4264.

Level 6: Descending Pain Modulation (Continued)

Quercetin influences descending pain modulatory systems through multiple neurotransmitter pathways:

[1-3]

Serotonergic Descending Modulation:

  • Quercetin’s analgesic effects involve the serotonergic system, as demonstrated by reversal with serotonin antagonists and synthesis inhibitors. Pretreatment with ketanserin (5-HT2A/2C antagonist), methysergide (non-selective 5-HT antagonist), or p-chlorophenylalanine (serotonin synthesis inhibitor) significantly attenuates quercetin-induced antinociception.[2]
  • In visceral pain models, quercetin attenuates 5-HT availability in the colon by reducing enterochromaffin cell density and tryptophan hydroxylase expression, modulating peripheral serotonergic signaling that contributes to visceral hypersensitivity.[3]
  • Quercetin inhibits MAO-A activity in brain mitochondria, potentially enhancing serotonergic tone in descending modulatory pathways originating from the rostral ventromedial medulla (RVM) and periaqueductal gray (PAG).[4]
  • Recent evidence suggests quercetin modulates serotonin transporter (SERT) function, which may influence serotonin availability in descending pain modulatory circuits.[5]

GABAergic Modulation:

  • Quercetin’s antinociceptive effects are mediated in part through GABAergic mechanisms. Both GABA(A) antagonist (bicuculline) and GABA(B) antagonist (baclofen) reverse quercetin-induced analgesia, indicating involvement of both receptor subtypes.[2]
  • Quercetin demonstrates binding affinity for GABA receptor subunits (α5, β1, β2), suggesting direct modulation of inhibitory neurotransmission in descending pathways.[6-7]
  • In silico molecular docking studies confirm quercetin’s interaction with GABA(A) receptor binding sites, supporting its role as a positive allosteric modulator of GABAergic inhibition.[6]

Opioidergic System:

  • Preclinical evidence suggests quercetin modulates the endogenous opioidergic system as part of its analgesic mechanism. The opioid antagonist naloxone partially reverses quercetin’s antinociceptive effects in some pain models, indicating involvement of endogenous opioid peptides.[1][8]
  • Quercetin may enhance descending opioidergic inhibition through interactions with μ-opioid receptors in the PAG-RVM axis.[1]

Nitric Oxide Pathway:

  • Quercetin’s antinociceptive action involves the L-arginine-nitric oxide pathway. Pretreatment with L-arginine (nitric oxide precursor) reverses quercetin-induced analgesia, while L-NAME (nitric oxide synthase inhibitor) potentiates its effects.[2]
  • This suggests quercetin may inhibit excessive nitric oxide production that contributes to central sensitization and impaired descending inhibition.[2][9]

Adrenergic Modulation:

  • The noradrenergic system, a key component of descending pain modulation, may also be influenced by quercetin. Noradrenergic projections from the locus coeruleus to the spinal cord dorsal horn provide inhibitory control over nociceptive transmission.[1]
  • Quercetin’s anti-inflammatory effects in brainstem nuclei may preserve noradrenergic neuron function and enhance descending inhibitory tone.[10]

Integrated Descending Modulation:

  • By modulating serotonergic, GABAergic, opioidergic, noradrenergic, and nitric oxide systems, quercetin may enhance descending inhibitory control over spinal nociceptive processing.[1-2]
  • The convergence of these mechanisms at the level of the spinal cord dorsal horn results in reduced excitability of wide dynamic range (WDR) neurons and decreased nociceptive transmission.[11]
  • Quercetin’s ability to reduce neuroinflammation in supraspinal structures (PAG, RVM, locus coeruleus) may restore impaired descending modulation that characterizes chronic pain states.[10][12]

Summary of Level 6 Effects:

Quercetin demonstrates multi-target modulation of descending pain pathways through:

  1. Enhancement of serotonergic inhibition via MAO-A inhibition and SERT modulation
  2. Potentiation of GABAergic inhibition through GABA(A) and GABA(B) receptor interactions
  3. Facilitation of endogenous opioidergic analgesia
  4. Modulation of nitric oxide signaling
  5. Preservation of noradrenergic descending inhibition through anti-neuroinflammatory effects

SUMMARY: Pain Processing Pathway Analysis

Quercetin demonstrates comprehensive effects across all six levels of pain processing:

Level

Primary Mechanisms

Key Targets

References

Level 1 (Peripheral Nociception)

Ion channel modulation, mast cell stabilization, COX-2 inhibition

TRPV1, Nav channels, K+ channels, P2X receptors, mast cells

[1], [2], [3]

Level 2 (Primary Afferent Transmission)

DRG neuron modulation, satellite glial cell inhibition

P2X4, PKCε, TNF-α-TNFR1-ERK1/2 pathway

[4], [5]

Level 3 (Spinal Cord Dorsal Horn)

Central sensitization inhibition, glial modulation, synaptic plasticity

mTOR/p70S6K, NF-κB, microglia, astrocytes, WDR neurons

[5], [6], [7], [8]

Level 4 (Ascending Pathways)

Neuroinflammation suppression, neuroprotection

NLRP3 inflammasome, Nrf2/HO-1, mitochondrial function

[5], [6]

Level 5 (Thalamic/Cortical Processing)

Neurotransmitter modulation, cortical neuroinflammation

5-HT, GABA receptors, MAO-A, NF-κB

[1], [8]

Level 6 (Descending Modulation)

Multi-neurotransmitter enhancement of inhibition

Serotonergic, GABAergic, opioidergic, NO pathways

[1]

This multi-level activity profile positions quercetin as a comprehensive modulator of pain processing, addressing both peripheral and central mechanisms of chronic pain. The evidence demonstrates that quercetin acts at peripheral nociceptors by blocking voltage-gated sodium channels and inhibiting COX-2, modulates dorsal root ganglion neurons through the TNF-α-TNFR1-ERK1/2 pathway, inhibits central sensitization in the spinal dorsal horn via mTOR/p70S6K pathway suppression and glial cell modulation, and enhances descending inhibitory pathways through multiple neurotransmitter systems.[2][3][5][6][7][1]

References for Table

  1. The Emerging Role of Quercetin in the Treatment of Chronic Pain. Liu C, Liu DQ, Tian YK, et al. Current Neuropharmacology. 2022;20(12):2346-2353. doi:10.2174/1570159X20666220812122437.
  2. Quercetin, Main Active Ingredient of Moutan Cortex, Alleviates Chronic Orofacial Pain via Block of Voltage-Gated Sodium Channel. Liu Z, Shan Z, Yang H, et al. Anesthesia and Analgesia. 2024;138(6):1324-1336. doi:10.1213/ANE.0000000000006730.
  3. Phytochemical Quercetin Alleviates Hyperexcitability of Trigeminal Nociceptive Neurons Associated With Inflammatory Hyperalgesia Comparable to NSAIDs. Itou H, Toyota R, Takeda M. Molecular Pain. 2022;18:17448069221108971. doi:10.1177/17448069221108971.
  4. Quercetin Alleviates Osteoarthritis Pain by Inhibiting Vascular Endothelial Growth Factor a Through Regulating cGAS/STING Pathway. Hu E, Wei Y, Liao T, et al. Journal of Cellular and Molecular Medicine. 2026;30(1):e70992. doi:10.1111/jcmm.70992.
  5. Quercetin Ameliorates CFA-Induced Chronic Inflammatory Hyperalgesia via Modulation of ROS-Mediated ERK1/2 Signaling and Inhibition of Spinal Glial Activation in Vivo. Kumar S, Vinayak M. Neuromolecular Medicine. 2020;22(4):517-533. doi:10.1007/s12017-020-08609-z.
  6. Quercetin Inhibits Peripheral and Spinal Cord Nociceptive Mechanisms to Reduce Intense Acute Swimming-Induced Muscle Pain in Mice. Borghi SM, Pinho-Ribeiro FA, Fattori V, et al. PloS One. 2016;11(9):e0162267. doi:10.1371/journal.pone.0162267.
  7. Quercetin Attenuates Diabetic Neuropathic Pain by Inhibiting mTOR/p70S6K Pathway-Mediated Changes of Synaptic Morphology and Synaptic Protein Levels in Spinal Dorsal Horn of Db/Db Mice. Wang R, Qiu Z, Wang G, et al. European Journal of Pharmacology. 2020;882:173266. doi:10.1016/j.ejphar.2020.173266.
  8. Quercetin Alleviates Thermal and Cold Hyperalgesia in a Rat Neuropathic Pain Model by Inhibiting Toll-Like Receptor Signaling. Ji C, Xu Y, Han F, et al. Biomedicine & Pharmacotherapy = Biomedecine & Pharmacotherapie. 2017;94:652-658. doi:10.1016/j.biopha.2017.07.145. 

This multi-level activity profile positions quercetin as a comprehensive modulator of pain processing, addressing both peripheral and central mechanisms of chronic pain.  [1][8][11]

 

 

Quercetin: Pain Processing Effects vs. Direct Tissue-Modifying Effects

Most nutraceuticals demonstrating benefit for pain provide both impact on pain processing as well as direct  impact on on damaged tissues as well. Some nutraceuticals will feature dominance with impact on pain processing effects as opposed to tissue-modifying effects while others are more balanced or the opposite.

Quercetin

   Pain Processing Effects:

Quercetin exerts analgesic effects through multiple convergent mechanisms targeting both peripheral and central pain processing. A comprehensive review summarizes that quercetin possesses anti-nociceptive effects in rodent models of inflammatory pain, neuropathic pain, and cancer pain via suppressing neuroinflammation and oxidative stress, modulating synaptic plasticity, GABAergic system, and opioidergic system.[1]

In diabetic neuropathic pain, quercetin alleviates thermal hyperalgesia by inhibiting mTOR/p70S6K pathway-mediated changes in synaptic morphology—reducing total dendritic length, dendritic branches, and spine density in spinal dorsal horn neurons, while decreasing synaptic plasticity-associated proteins PSD-95 and synaptophysin.[2] Quercetin also inhibits upregulated P2X4 receptors in DRG satellite glial cells, subsequently inhibiting P2X4 receptor-mediated p38MAPK activation to relieve mechanical and thermal hyperalgesia in diabetic rats.[3]

In inflammatory pain models (CFA-induced), quercetin ameliorates chronic inflammatory hyperalgesia via modulation of ROS-mediated ERK1/2 signaling and inhibition of spinal glial activation. Quercetin attenuates the TNF-α-TNFR1-ERK1/2 pathway, reduces NF-κB activation in DRG and spinal cord, and suppresses microglial (Iba1) and astrocyte (GFAP) activation.[4]

Quercetin alleviates neuropathic pain by inhibiting Toll-like receptor signaling—reducing phosphorylation of TAK1, IKK, and JNK2, and dose-dependently inhibiting NF-κB activity via TAK1. Both single and continuous oral administration dose-dependently alleviated SNL-induced thermal and cold hyperalgesia, with pre-administration also attenuating neuropathic pain symptoms.[5]

In diabetic peripheral neuropathy, quercetin (30-60 mg/kg/day for 6 weeks) improved mechanical withdrawal threshold and nerve conduction velocity, and reduced TNF-α and IL-1β levels by downregulating the TLR4/MyD88/NF-κB signaling pathway in sciatic nerves—effects independent of blood glucose levels.[6]

A 2026 study demonstrated that quercetin alleviates OA pain by inhibiting the cGAS/STING pathway, leading to downregulation of VEGFA, VEGFR1, and phosphorylated VEGFR1, with reduced peripheral inflammatory and nociceptive markers and diminished pain hypersensitivity.[7]

    Clinical Evidence for Pain Processing:

A double-blind, randomized, placebo-controlled trial in 50 women with rheumatoid arthritis found that quercetin 500 mg/day for 8 weeks significantly reduced early morning stiffness, morning pain, and after-activity pain (p < 0.05). DAS-28 and HAQ scores decreased, the number of patients with active disease significantly decreased, and plasma hs-TNFα was significantly reduced compared to placebo.[8]

A combination supplement containing glucosamine, chondroitin sulfate, and quercetin glycosides (45 mg/day) in a 16-week RCT of 40 Japanese subjects with knee OA showed significantly improved symptom/function subscale scores and a trend toward improved type II collagen synthesis/degradation balance.[9]

   Direct Tissue-Modifying Effects:

Quercetin demonstrates robust chondroprotective effects across multiple preclinical models. A 2023 systematic review and meta-analysis of 12 in vivo animal studies found that quercetin significantly improved OA cartilage OARSI scores (SMD -6.30, 95% CI -9.59 to -3.01, p = 0.0002), with all studies supporting quercetin’s protective effects against OA during disease and aging.[10]

Mechanistically, quercetin exerts chondroprotection through multiple pathways:

  1. SIRT1/Nrf2/HO-1 pathway activation: Quercetin inhibits chondrocyte ferroptosis, reduces oxidative damage, decreases serum IL-1β, TNF-α, MMP3, CTX-II, and COMP, and normalizes abnormal subchondral bone remodeling.[11]
  2. SIRT1/AMPK-mediated ER stress inhibition: Quercetin attenuates oxidative stress-induced apoptosis, abolishes cartilage degeneration, and decreases chondrocyte apoptosis in knee joints.[12]
  3. AMPK/Nrf2/Gpx4 ferroptosis suppression: Quercetin promotes chondrocyte proliferation, reduces apoptosis and inflammation, inhibits ECM degradation, and ameliorates articular cartilage destruction.[13]
  4. Macrophage polarization modulation: Quercetin induces M2 polarization of synovial macrophages, upregulates TGF-β and IGF, creating a pro-chondrogenic microenvironment that promotes GAG synthesis.[14]
  5. TRPV1-mediated P2X7/NLRP3 pathway blockade: Quercetin decreases M1-polarized macrophages, shifting macrophage polarization from M1 to M2 subtypes.[15]  Intra-articular quercetin injection alleviated cartilage degradation and chondrocyte apoptosis in rat OA models, with elevated TGF-β1/β2 in synovial fluid and increased M2 macrophage ratio in synovial membrane.[14]

   Bioavailability Considerations:

A 2025 systematic review of 31 human intervention studies found that quercetin aglycone has very poor bioavailability (~20-fold lower than quercetin-3-O-oligoglucosides). Enhanced formulations significantly improve absorption: quercetin-3-O-glucoside-γ-cyclodextrin complex showed 10.8-fold increase, self-emulsifying fenugreek galactomannans/lecithin encapsulation showed 62-fold increase, and lecithin phytosome showed 20.1-fold increase in bioavailability.[16]

A pharmacokinetic study found that LipoMicel® formulation increased quercetin blood concentrations by 7-fold at the same dose and 15-fold at double dose compared to standard quercetin.[17]

Mechanism

Pain Processing

Tissue Modification

References

mTOR/p70S6K inhibition → synaptic remodeling

↓Dendritic length/branches/spines in spinal dorsal horn; ↓PSD-95, synaptophysin

None

[1]

P2X4 receptor inhibition in DRG SGCs

↓p38MAPK activation; relieves mechanical/thermal hyperalgesia

None

[2]

TLR4/MyD88/NF-κB pathway inhibition

↓TNF-α, IL-1β in sciatic nerve; improves nerve conduction

Indirect

[3]

ROS/ERK1/2 modulation + glial inhibition

↓Spinal microglial/astrocyte activation; ↓central sensitization

None

[4]

cGAS/STING pathway inhibition

↓VEGFA/VEGFR1; ↓peripheral nociceptive markers

Preserves cartilage morphology

[5]

SIRT1/Nrf2/HO-1 activation

Indirect (antioxidant)

↓Ferroptosis; ↓MMP3/13; ↓CTX-II, COMP

[6]

SIRT1/AMPK → ER stress inhibition

Indirect

↓Chondrocyte apoptosis; ↓cartilage degeneration

[7]

M1→M2 macrophage polarization

↓Synovial inflammation

↑TGF-β, IGF; ↑GAG synthesis; pro-chondrogenic environment

[8]

 

References

  1. The Emerging Role of Quercetin in the Treatment of Chronic Pain. Liu C, Liu DQ, Tian YK, et al. Current Neuropharmacology. 2022;20(12):2346-2353. doi:10.2174/1570159X20666220812122437.
  2. Quercetin Attenuates Diabetic Neuropathic Pain by Inhibiting mTOR/p70S6K Pathway-Mediated Changes of Synaptic Morphology and Synaptic Protein Levels in Spinal Dorsal Horn of Db/Db Mice. Wang R, Qiu Z, Wang G, et al. European Journal of Pharmacology. 2020;882:173266. doi:10.1016/j.ejphar.2020.173266.
  3. Quercetin Relieved Diabetic Neuropathic Pain by Inhibiting Upregulated P2X Receptor in Dorsal Root Ganglia. Yang R, Li L, Yuan H, et al. Journal of Cellular Physiology. 2019;234(3):2756-2764. doi:10.1002/jcp.27091.
  4. Quercetin Ameliorates CFA-Induced Chronic Inflammatory Hyperalgesia via Modulation of ROS-Mediated ERK1/2 Signaling and Inhibition of Spinal Glial Activation in Vivo. Kumar S, Vinayak M. Neuromolecular Medicine. 2020;22(4):517-533. doi:10.1007/s12017-020-08609-z.
  5. Quercetin Alleviates Thermal and Cold Hyperalgesia in a Rat Neuropathic Pain Model by Inhibiting Toll-Like Receptor Signaling. Ji C, Xu Y, Han F, et al. Biomedicine & Pharmacotherapy = Biomedecine & Pharmacotherapie. 2017;94:652-658. doi:10.1016/j.biopha.2017.07.145.
  6. Quercetin Reduces Inflammation in a Rat Model of Diabetic Peripheral Neuropathy by Regulating the TLR4/MyD88/NF-κB Signalling Pathway. Zhao B, Zhang Q, Liang X, Xie J, Sun Q. European Journal of Pharmacology. 2021;912:174607. doi:10.1016/j.ejphar.2021.174607.
  7. Quercetin Alleviates Osteoarthritis Pain by Inhibiting Vascular Endothelial Growth Factor a Through Regulating cGAS/STING Pathway. Hu E, Wei Y, Liao T, et al. Journal of Cellular and Molecular Medicine. 2026;30(1):e70992. doi:10.1111/jcmm.70992.
  8. The Effect of Quercetin on Inflammatory Factors and Clinical Symptoms in Women With Rheumatoid Arthritis: A Double-Blind, Randomized Controlled Trial. Javadi F, Ahmadzadeh A, Eghtesadi S, et al. Journal of the American College of Nutrition. 2017;36(1):9-15. doi:10.1080/07315724.2016.1140093.
  9. Effect of a Dietary Supplement Containing Glucosamine Hydrochloride, Chondroitin Sulfate and Quercetin Glycosides on Symptomatic Knee Osteoarthritis: A Randomized, Double-Blind, Placebo-Controlled Study. Kanzaki N, Saito K, Maeda A, et al. Journal of the Science of Food and Agriculture. 2012;92(4):862-9. doi:10.1002/jsfa.4660.
  10. Therapeutic Potential of Senolytic Agent Quercetin in Osteoarthritis: A Systematic Review and Meta-Analysis of Preclinical Studies. Yamaura K, Nelson AL, Nishimura H, et al. Ageing Research Reviews. 2023;90:101989. doi:10.1016/j.arr.2023.101989.
  11. Quercetin Modulates Ferroptosis via the SIRT1/Nrf-2/HO-1 Pathway and Attenuates Cartilage Destruction in an Osteoarthritis Rat Model. Ruan H, Zhu T, Wang T, et al. International Journal of Molecular Sciences. 2024;25(13):7461. doi:10.3390/ijms25137461.
  12. Quercetin Attenuates Oxidative Stress-Induced Apoptosis via SIRT1/AMPK-mediated Inhibition of ER Stress in Rat Chondrocytes and Prevents the Progression of Osteoarthritis in a Rat Model. Feng K, Chen Z, Pengcheng L, Zhang S, Wang X. Journal of Cellular Physiology. 2019;234(10):18192-18205. doi:10.1002/jcp.28452.
  13. Quercetin Attenuates the Symptoms of Osteoarthritis in Vitro and in Vivo by Suppressing Ferroptosis via Activation of AMPK/Nrf2/Gpx4 Signaling. Dong S, Li X, Xu G, Chen L, Zhao J. Molecular Medicine Reports. 2025;31(3):60. doi:10.3892/mmr.2024.13425.
  14. Quercetin Alleviates Rat Osteoarthritis by Inhibiting Inflammation and Apoptosis of Chondrocytes, Modulating Synovial Macrophages Polarization to M2 Macrophages. Hu Y, Gui Z, Zhou Y, et al. Free Radical Biology & Medicine. 2019;145:146-160. doi:10.1016/j.freeradbiomed.2019.09.024.
  15. Quercetin as a Promising Intervention for Rat Osteoarthritis by Decreasing M1-Polarized Macrophages via Blocking the TRPV1-mediated P2x7/Nlrp3 Signaling Pathway. Li W, He H, Du M, et al. Phytotherapy Research : PTR. 2024;38(4):1990-2006. doi:10.1002/ptr.8158.
  16. Improving Quercetin Bioavailability: A Systematic Review and Meta-Analysis of Human Intervention Studies. Liu L, Barber E, Kellow NJ, Williamson G. Food Chemistry. 2025;477:143630. doi:10.1016/j.foodchem.2025.143630.
  17. A Pharmacokinetic Study of Different Quercetin Formulations in Healthy Participants: A Diet-Controlled, Crossover, Single- And Multiple-Dose Pilot Study. Solnier J, Zhang Y, Roh K, et al. Evidence-Based Complementary and Alternative Medicine : eCAM. 2023;2023:9727539. doi:10.1155/2023/9727539.

 

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