Safety Reading Notes

Read safety context beside the research guide.

The GPR18 source set should still be read with safety context in mind. Mechanistic or preclinical evidence should not be converted into consumer instructions, and product identity can change how closely a source applies. PMID 34676329

PubMed For Dummies Article

GPR18 Evidence Review: the long-form source walk-through

Quick read
  • GPR18 currently has 28 source-backed evidence row(s), so this page should be read as a research guide rather than a single conclusion. PMID 34676329
  • The evidence classes most visible in the row language are insufficient (14), mechanistic or pharmacological (13), and preclinical (1). PMID 31146657
  • The study-design language most visible in the row language is Narrative or expert review (14), Cellular or in vitro study (8), and Animal study (5). PMID 30670965
  • The repeated topics are GPR18 (19), receptor, target, or pharmacology mechanisms (5), GPR55 (2), CB1 (1), and other mapped categories (1), which tells the reader where to start opening PubMed and DOI links. PMID 28826536

Start with the research question

GPR18 is built from 28 source-backed evidence row(s) and 24 research source(s). The current evidence classes read as insufficient (14), mechanistic or pharmacological (13), and preclinical (1), and the study-design language most often reads as Narrative or expert review (14), Cellular or in vitro study (8), and Animal study (5). PMID 34676329

The row-level question is not simply whether GPR18 is "good" or "bad." The useful question is what each row studied, what evidence class it received, and whether the source is close to the reader's actual question. The most repeated row topics are GPR18 (19), receptor, target, or pharmacology mechanisms (5), GPR55 (2), CB1 (1), and other mapped categories (1). PMID 20346144

Human evidence 0 rows

Rows involving human participants, patients, or clinical source language. These rows are closer to everyday reader questions, but still depend on population, dose, route, comparator, and endpoint. PMID 30767756

Preclinical evidence 1 row

Animal, cellular, or model-based rows. These can explain why a topic is being studied, but they should not be read as human-health instructions. PMID 30550613

Mechanistic evidence 13 rows

Rows about receptors, enzymes, channels, metabolism, binding, signaling, or pharmacology. These explain plausibility without proving a consumer outcome. PMID 27835801

Limits and uncertainty 14 rows

Rows where safety, tolerability, risk, product limits, or insufficient evidence need to stay visible next to the rest of the article. PMID 32365486

The lane labels are not a quality score. They are a reading method: keep human evidence, preclinical evidence, mechanisms, and uncertainty in separate mental boxes before deciding what a source can actually support. PMID 42114685

Where this page has the most source density

The largest bucket surfaced for this page is GPR18. That does not automatically mean the topic is settled; it means this is where the current source trail is densest. The next visible bucket is GPR18, which gives readers another way to see what the literature repeatedly circles. PMID 34676329

Source density should be read with evidence posture. A bucket can contain many rows and still be limited if the studies are indirect, mixed, preclinical, product-specific, or mostly review-level. The paragraphs below name the buckets directly and keep each explanation connected to a source record. PMID 20346144

Bucket chapters: what the literature is circling

GPR18

7 research sources 7 rows (947-961) Mechanistic research summary: insufficient (5), mechanistic or pharmacological (2)

GPR18 appears in rows about GPR18 mechanisms. It currently draws from 7 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 34676329

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 34676329

  • Evidence row 947

    Endocannabinoids modulates GPR18; evidence class: insufficient (study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 34676329

  • Evidence row 961

    Endocannabinoids modulates GPR18; evidence class: insufficient (population or model: Animal model mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 18187165

GPR18

5 research sources 5 rows (955-962) Mechanistic research summary: mechanistic or pharmacological (5)

GPR18 appears in rows about GPR18 mechanisms. It currently draws from 5 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 20346144

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 20346144

  • Evidence row 955

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Cellular or in vitro model mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signal... PMID 20346144

  • Evidence row 962

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Animal study; outcome measure: GPR18 receptor activity, binding, signaling, or ph... PMID 24751709

GPR18

4 research sources 4 rows (946-957) Mechanistic research summary: mechanistic or pharmacological (4)

GPR18 appears in rows about GPR18 mechanisms. It currently draws from 4 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 32365486

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 32365486

  • Evidence row 946

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, si... PMID 32365486

  • Evidence row 957

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, si... PMID 21595653

GPR18

3 research sources 3 rows (944-951) Mechanistic research summary: insufficient (2), mechanistic or pharmacological (1)

GPR18 appears in rows about GPR18 mechanisms. It currently draws from 3 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 28826536

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 28826536

  • Evidence row 944

    Cannabinoids modulates GPR18; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling,... PMID 28826536

  • Evidence row 951

    Cannabinoids modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 40562148

GPR55

2 research sources 2 rows (926-933) Mapped evidence with interpretation limits: insufficient (2)

GPR18 appears in rows about GPR55 mechanisms. It currently draws from 2 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 28826536

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 28826536

  • Evidence row 926

    Cannabinoids modulates GPR55; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR55 receptor activity, binding, signaling,... PMID 28826536

  • Evidence row 933

    Cannabinoids modulates GPR55; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR55 receptor activity, binding, signaling,... PMID 27835801

receptor, target, or pharmacology mechanisms

2 research sources 2 rows (211-212) Mapped evidence with interpretation limits: insufficient (2)

GPR18 appears in rows about receptor, target, or pharmacology mechanisms mechanisms. It currently draws from 2 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 28826536

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 28826536

  • Evidence row 211

    Cannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: recept... PMID 28826536

  • Evidence row 212

    Cannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 30767756

receptor, target, or pharmacology mechanisms

2 research sources 2 rows (209-210) Mapped evidence with interpretation limits: insufficient (2)

GPR18 appears in rows about receptor, target, or pharmacology mechanisms mechanisms. It currently draws from 2 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 31146657

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 31146657

  • Evidence row 209

    Endocannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: re... PMID 31146657

  • Evidence row 210

    Endocannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 30670965

CB1

1 research source 839 Mapped evidence with interpretation limits: insufficient (1)

GPR18 appears in rows about CB1 mechanisms. It currently draws from 1 research source(s), and mechanistic evidence should stay separate from human-outcome evidence. PMID 30767756

Read this bucket as mechanism or pharmacology context. Mechanisms can make the biology easier to understand, but they are not the same thing as a demonstrated effect in people. PMID 30767756

  • Evidence row 839

    Cannabinoids modulates CB1; evidence class: insufficient (study design: Narrative or expert review; outcome measure: CB1 neurobehavioral, appetite, metabolic, pain, cognition, or synaptic mechanisms). PMID 30767756

Human evidence, mechanisms, and safety are different lanes

This page currently separates human evidence (0 row(s)), mechanistic evidence (13 row(s)), and safety/tolerability context (0 row(s)). That separation is the heart of the site. Mechanistic evidence can make a topic biologically interesting, but it should not silently become a human outcome. PMID 34676329

Human evidence still depends on population, dose, route, duration, product identity, and endpoint. Safety rows belong in the same reading path as benefit-oriented rows because formulation, co-exposures, prescription medications, impairment context, and higher-risk populations can change how close a source is to a reader's question. PMID 20346144

What this does and does not mean

  • It means the page has a traceable source trail. It does not mean every bucket has the same clinical strength. PMID 29902723
  • It means mechanisms, animal models, human studies, safety rows, and insufficient-evidence rows are being kept visible as separate evidence types. PMID 24762058
  • It does not turn a preclinical mechanism into a consumer recommendation, and it does not treat one product, dose, route, or population as interchangeable with another. PMID 40562148

How to use the source table

The source-backed evidence table below is the audit trail. Each row keeps a public sentence connected to a source record when a PubMed ID or DOI is available. If a sentence feels important, the reader should be able to click through, inspect the study type, and decide whether the source is close to the question they care about. PMID 34676329

This is why the public page is intentionally layered. The top gives the reader a fast orientation. The bucket table groups repeated rows into readable topics. The article body explains the buckets using the actual evidence-row language. The source notes below walk through every evidence row before the source table repeats the technical trace. PMID 20346144

Source-reading checklist for GPR18

  1. Open the linked PubMed or DOI record. PMID 29098189
  2. Check whether the source studied humans, animals, cells, chemistry, pharmacology, product testing, or a review of prior literature. PMID 27018161
  3. Compare the source product, dose, route, population, and endpoint to the question being asked. PMID 30871175
  4. Look for safety, tolerability, drug-interaction, impairment, pregnancy, pediatric, psychiatric, cardiovascular, and product-quality context before treating the bucket as settled. PMID 20346144
  5. Return to the evidence table when the article summary sounds too broad; the row is the audit unit. PMID 22834922

Source Notes

GPR18 source-by-source reading notes

These notes pull every evidence row on this page into the readable article body before the source table repeats the audit trail. Each note keeps the row language beside the PubMed or DOI link when available.

  1. Evidence row 209

    Endocannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 31146657

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Potential metabolic and behavioural roles of the putative endocannabinoid receptors GPR18, GPR55 and GPR119 in feeding.
  2. Evidence row 210

    Endocannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 30670965

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Some Prospective Alternatives for Treating Pain: The Endocannabinoid System and Its Putative Receptors GPR18 and GPR55.
  3. Evidence row 211

    Cannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 28826536

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors.
  4. Evidence row 212

    Cannabinoids modulates receptor, target, or pharmacology mechanisms; evidence class: insufficient (study design: Narrative or expert review; outcome measure: receptor, target, or pharmacology mechanisms). PMID 30767756

    Evidence class: insufficient; Study design: Narrative or expert review. Source: New Insights in Cannabinoid Receptor Structure and Signaling.
  5. Evidence row 213

    THC modulates receptor, target, or pharmacology mechanisms; evidence class: preclinical (population or model: Animal model mentioned; study design: Animal study; outcome measure: receptor, target, or pharmacology mechanisms). PMID 30550613

    Evidence class: preclinical; Study design: Animal study. Source: Δ9-Tetrahydrocannabinol and Cannabidiol Differentially Regulate Intraocular Pressure.
  6. Evidence row 839

    Cannabinoids modulates CB1; evidence class: insufficient (study design: Narrative or expert review; outcome measure: CB1 neurobehavioral, appetite, metabolic, pain, cognition, or synaptic mechanisms). PMID 30767756

    Evidence class: insufficient; Study design: Narrative or expert review. Source: New Insights in Cannabinoid Receptor Structure and Signaling.
  7. Evidence row 926

    Cannabinoids modulates GPR55; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR55 receptor activity, binding, signaling, or pharmacology). PMID 28826536

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors.
  8. Evidence row 933

    Cannabinoids modulates GPR55; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR55 receptor activity, binding, signaling, or pharmacology). PMID 27835801

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoid receptor ligand bias: implications in the central nervous system.
  9. Evidence row 944

    Cannabinoids modulates GPR18; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 28826536

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors.
  10. Evidence row 945

    Cannabinoids modulates GPR18; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 27835801

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoid receptor ligand bias: implications in the central nervous system.
  11. Evidence row 946

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 32365486

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: Computational Investigations on the Binding Mode of Ligands for the Cannabinoid-Activated G Protein-Coupled Receptor GPR18.
  12. Evidence row 947

    Endocannabinoids modulates GPR18; evidence class: insufficient (study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 34676329

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Cannabinoids in Gynecological Diseases.
  13. Evidence row 948

    Endocannabinoids modulates GPR18; evidence class: insufficient (population or model: Human participants or patients mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 42114685

    Evidence class: insufficient; Study design: Narrative or expert review. Source: Targeting GPR18: Structural modelling, ligand discovery, and therapeutic potential in neuroinflammatory disorders.
  14. Evidence row 949

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 29902723

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: Structure-activity relationships of imidazothiazinones and analogs as antagonists of the cannabinoid-activated orphan G protein-coupled receptor GPR18.
  15. Evidence row 950

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Cellular or in vitro model mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 24762058

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: Activation of GPR18 by cannabinoid compounds: a tale of biased agonism.
  16. Evidence row 951

    Cannabinoids modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 40562148

    Evidence class: mechanistic or pharmacological. Source: Structural insights into the activation of G protein-coupled receptor 119 by the agonist GSK1292263 and ligands selectivity among novel cannabinoid receptors.
  17. Evidence row 952

    Endocannabinoids modulates GPR18; evidence class: insufficient (population or model: Cellular or in vitro model mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 29098189

    Evidence class: insufficient; Study design: Narrative or expert review. Source: An Update on Non-CB1, Non-CB2 Cannabinoid Related G-Protein-Coupled Receptors.
  18. Evidence row 953

    Endocannabinoids modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Cellular or in vitro model mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 27018161

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: GPR18 undergoes a high degree of constitutive trafficking but is unresponsive to N-Arachidonoyl Glycine.
  19. Evidence row 954

    Endocannabinoids modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Animal model mentioned; study design: Animal study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 30871175

    Evidence class: mechanistic or pharmacological; Study design: Animal study. Source: Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures.
  20. Evidence row 955

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Cellular or in vitro model mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 20346144

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: N-arachidonoyl glycine, an abundant endogenous lipid, potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor.
  21. Evidence row 956

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 22834922

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: siRNA knockdown of GPR18 receptors in BV-2 microglia attenuates N-arachidonoyl glycine-induced cell migration.
  22. Evidence row 957

    THC modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 21595653

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: Δ(9) -Tetrahydrocannabinol and N-arachidonyl glycine are full agonists at GPR18 receptors and induce migration in human endometrial HEC-1B cells.
  23. Evidence row 958

    Endocannabinoids modulates GPR18; evidence class: insufficient (study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 29138268

    Evidence class: insufficient; Study design: Narrative or expert review. Source: N-Acyl Amino Acids (Elmiric Acids): Endogenous Signaling Molecules with Therapeutic Potential.
  24. Evidence row 959

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Animal model mentioned; study design: Animal study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 23461720

    Evidence class: mechanistic or pharmacological; Study design: Animal study. Source: A GPR18-based signalling system regulates IOP in murine eye.
  25. Evidence row 960

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Animal model mentioned; study design: Animal study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 24431468

    Evidence class: mechanistic or pharmacological; Study design: Animal study. Source: The novel endocannabinoid receptor GPR18 is expressed in the rostral ventrolateral medulla and exerts tonic restraining influence on blood pressure.
  26. Evidence row 961

    Endocannabinoids modulates GPR18; evidence class: insufficient (population or model: Animal model mentioned; study design: Narrative or expert review; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 18187165

    Evidence class: insufficient; Study design: Narrative or expert review. Source: The elmiric acids: biologically active anandamide analogs.
  27. Evidence row 962

    CBD modulates GPR18; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Animal study; outcome measure: GPR18 receptor activity, binding, signaling, or pharmacology). PMID 24751709

    Evidence class: mechanistic or pharmacological; Study design: Animal study. Source: Cannabinoid and lipid-mediated vasorelaxation in retinal microvasculature.
  28. Evidence row 1134

    NADA studied for NADA biology, receptor or TRP-channel pharmacology, metabolism, physiology, or safety-relevant mechanisms; evidence class: mechanistic or pharmacological (population or model: Human participants or patients mentioned; study design: Cellular or in vitro study; outcome measure: NADA biology, receptor or TRP-channel pharmacology, metabolism, physiology, or safety-relevant mechanisms). PMID 24644287

    Evidence class: mechanistic or pharmacological; Study design: Cellular or in vitro study. Source: The endocannabinoid/endovanilloid N-arachidonoyl dopamine (NADA) and synthetic cannabinoid WIN55,212-2 abate the inflammatory activation of human endothelial cells.