Cannabinoid Encyclopedia

How cannabinoids work

What is GPR18?

A simple explanation of GPR18, why cannabinoid researchers study it, and what its biology can and cannot tell us.

Updated July 2026 19 research sources Mostly early-stage research

The short answer

Where GPR18 fits into cannabinoid biology

GPR18 is a biological target studied to understand how cannabinoids affect cells and signaling. Research on CBD, THC, Cannabinoids, and Endocannabinoids helps explain possible mechanisms. This page brings together 6 human-study sources, 7 research reviews, and 6 lab, animal, or mechanism sources. Most of the current evidence is preclinical or focused on biological mechanisms. A mechanism alone does not prove that a cannabinoid will produce a health benefit in people. 1

Choose your next step

Want the quick path or the full picture?

Use this guide the way you need to. Start with the practical question, then open the study detail only when it helps answer something about GPR18.

What researchers studiedSee the main areas and the evidence behind each one. Safety and limitsKeep product, dose, medications, and context in view. Open the sourcesGo directly to the studies and references used here.

Key takeaways

What to know first

  1. 1

    Research on GPR18 covers CBD, THC, and Cannabinoids; those areas should not be combined into one claim. 1

  2. 2

    Most of the current evidence is preclinical or focused on biological mechanisms. 2

  3. 3

    Dose, formulation, route, study population, and outcome can change how closely a study applies to a real-world question. 3

Research areas

What researchers studied about GPR18

These are the main questions represented in the current literature. Each link opens a source used to build the overview.

Mostly mechanism-focused

CBD

Studies examine how CBD connects with GPR18 or closely related target biology. These findings help explain signaling and pharmacology, not a guaranteed health effect. 2

Mostly mechanism-focused

THC

Studies examine how THC connects with GPR18 or closely related target biology. These findings help explain signaling and pharmacology, not a guaranteed health effect. 3

Mostly mechanism-focused

Cannabinoids

Studies examine how Cannabinoids connects with GPR18 or closely related target biology. These findings help explain signaling and pharmacology, not a guaranteed health effect. 4

Mostly mechanism-focused

Endocannabinoids

Studies examine how Endocannabinoids connects with GPR18 or closely related target biology. These findings help explain signaling and pharmacology, not a guaranteed health effect. 5

How strong is the research?

Not every study answers the same question

This page separates research in people, research reviews, and earlier-stage biology before interpreting the larger question.

6 sources

Human studies

Research involving people is closest to everyday health questions. The product, dose, population, and outcome still determine what each study can show.

7 sources

Reviews and evidence summaries

Reviews can compare several studies at once. Their conclusion is only as strong and as relevant as the studies they include.

6 sources

Lab, animal, and mechanism research

Early-stage research can explain biological interest. It cannot, by itself, show that the same effect happens in people.

What these studies actually looked at

The research on GPR18 is not one kind of study. This source set includes 7 cell or laboratory studies, 7 narrative or expert reviews, and 4 animal studies. 3

The recorded populations or models include people or patients (9 sources), animal models (4 sources), and cells or tissue models (4 sources). A result from one group or model should not be assumed to apply to another. 4

The most common recorded outcome focus is gPR18 receptor activity, binding, signaling, or pharmacology (19 sources). Closely related outcome names can still describe different measurements. 5

The GPR18 source set also contains findings or reviews that remain too limited, indirect, or mixed for a broad answer. That uncertainty is part of the result, not an empty space to fill with assumptions. 6

Examples from the literature

What did the studies actually look at?

Each example names the research question and the study details recorded for that source.

narrative or expert review

Targeting GPR18: Structural modelling, ligand discovery, and therapeutic potential in neuroinflammatory disorders.

On this page, this source examines Endocannabinoids activity involving GPR18. 1

Study type
narrative or expert review
Population or model
people or patients
Outcome focus
gPR18 receptor activity, binding, signaling, or pharmacology
Evidence stage
evidence still limited

cell or laboratory study

N-arachidonoyl glycine, an abundant endogenous lipid, potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor.

On this page, this source examines CBD activity involving GPR18. 2

Study type
cell or laboratory study
Population or model
cells or tissue models
Outcome focus
gPR18 receptor activity, binding, signaling, or pharmacology
Evidence stage
mechanism-focused research

cell or laboratory study

Computational Investigations on the Binding Mode of Ligands for the Cannabinoid-Activated G Protein-Coupled Receptor GPR18.

On this page, this source examines THC activity involving GPR18. 3

Study type
cell or laboratory study
Population or model
people or patients
Outcome focus
gPR18 receptor activity, binding, signaling, or pharmacology
Evidence stage
mechanism-focused research

narrative or expert review

Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors.

On this page, this source examines Cannabinoids activity involving GPR18. 4

Study type
narrative or expert review
Population or model
people or patients
Outcome focus
gPR18 receptor activity, binding, signaling, or pharmacology
Evidence stage
evidence still limited

narrative or expert review

Cannabinoids in Gynecological Diseases.

On this page, this source examines Endocannabinoids activity involving GPR18. 5

Study type
narrative or expert review
Outcome focus
gPR18 receptor activity, binding, signaling, or pharmacology
Evidence stage
evidence still limited

Safety and limits

What should readers keep in mind?

Research on GPR18 should be read beside safety. A compound can be non-intoxicating or naturally occurring and still have pharmacologic effects, side effects, interactions, or product-quality concerns. 2

Research doses are descriptions of what a study tested. They are not personal dosing instructions. Questions involving medications, pregnancy, children, driving, liver health, heart health, or serious symptoms deserve professional medical guidance.

Drug interactions Pregnancy and children Driving and impairment All safety topics

Common questions

Questions people ask

What does GPR18 do?

GPR18 is studied as part of cannabinoid-related biology and signaling. The exact role depends on the tissue, compound, and experimental setting. 7

Does a biological mechanism prove a health effect?

No. A mechanism can explain why an idea is plausible, but human studies are needed to test whether it changes a health outcome. 8

What research is linked to GPR18?

The main areas on this page include CBD, THC, Cannabinoids, and Endocannabinoids. The source links show the study type behind each area. 9

Sources

Read the research

The numbered sources below support the main overview. Links open the PubMed record or DOI in a new tab.

  1. 1
    Targeting GPR18: Structural modelling, ligand discovery, and therapeutic potential in neuroinflammatory disorders. narrative or expert review; evidence still limited PubMed 42114685 DOI 10.1016/j.bcp.2026.118038
  2. 2
    N-arachidonoyl glycine, an abundant endogenous lipid, potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor. cell or laboratory study; mechanism-focused research PubMed 20346144 DOI 10.1186/1471-2202-11-44
  3. 3
    Computational Investigations on the Binding Mode of Ligands for the Cannabinoid-Activated G Protein-Coupled Receptor GPR18. cell or laboratory study; mechanism-focused research PubMed 32365486 DOI 10.3390/biom10050686
  4. 4
    Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors. narrative or expert review; evidence still limited PubMed 28826536 DOI 10.1016/bs.apha.2017.04.004
  5. 5
    Cannabinoids in Gynecological Diseases. narrative or expert review; evidence still limited PubMed 34676329 DOI 10.1159/000499164
  6. 6
    An Update on Non-CB1, Non-CB2 Cannabinoid Related G-Protein-Coupled Receptors. narrative or expert review; evidence still limited PubMed 29098189 DOI 10.1089/can.2017.0036
  7. 7
    Cannabinoid receptor ligand bias: implications in the central nervous system. narrative or expert review; evidence still limited PubMed 27835801 DOI 10.1016/j.coph.2016.10.005
  8. 8
    N-Acyl Amino Acids (Elmiric Acids): Endogenous Signaling Molecules with Therapeutic Potential. narrative or expert review; evidence still limited PubMed 29138268 DOI 10.1124/mol.117.110841
  9. 9
    The elmiric acids: biologically active anandamide analogs. narrative or expert review; evidence still limited PubMed 18187165 DOI 10.1016/j.neuropharm.2007.11.011
  10. 10
    A GPR18-based signalling system regulates IOP in murine eye. animal study; mechanism-focused research PubMed 23461720 DOI 10.1111/bph.12136
  11. 11
    Cannabinoid and lipid-mediated vasorelaxation in retinal microvasculature. animal study; mechanism-focused research PubMed 24751709 DOI 10.1016/j.ejphar.2014.03.055
  12. 12
    Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures. animal study; mechanism-focused research PubMed 30871175 DOI 10.3390/ijms20061266
See all 19 research sources

This complete source list is the deeper research layer for the page. Study type and evidence context are shown when they are available in the current record.

  1. Cannabinoid Receptor-Related Orphan G Protein-Coupled Receptors. narrative or expert review; evidence still limited / 1 linked research note PubMed 28826536
  2. Cannabinoid receptor ligand bias: implications in the central nervous system. narrative or expert review; evidence still limited / 1 linked research note PubMed 27835801
  3. Computational Investigations on the Binding Mode of Ligands for the Cannabinoid-Activated G Protein-Coupled Receptor GPR18. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 32365486
  4. Cannabinoids in Gynecological Diseases. narrative or expert review; evidence still limited / 1 linked research note PubMed 34676329
  5. Targeting GPR18: Structural modelling, ligand discovery, and therapeutic potential in neuroinflammatory disorders. narrative or expert review; evidence still limited / 1 linked research note PubMed 42114685
  6. Structure-activity relationships of imidazothiazinones and analogs as antagonists of the cannabinoid-activated orphan G protein-coupled receptor GPR18. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 29902723
  7. Activation of GPR18 by cannabinoid compounds: a tale of biased agonism. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 24762058
  8. Structural insights into the activation of G protein-coupled receptor 119 by the agonist GSK1292263 and ligands selectivity among novel cannabinoid receptors. mechanism-focused research / 1 linked research note PubMed 40562148
  9. An Update on Non-CB1, Non-CB2 Cannabinoid Related G-Protein-Coupled Receptors. narrative or expert review; evidence still limited / 1 linked research note PubMed 29098189
  10. GPR18 undergoes a high degree of constitutive trafficking but is unresponsive to N-Arachidonoyl Glycine. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 27018161
  11. Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures. animal study; mechanism-focused research / 1 linked research note PubMed 30871175
  12. N-arachidonoyl glycine, an abundant endogenous lipid, potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 20346144
  13. siRNA knockdown of GPR18 receptors in BV-2 microglia attenuates N-arachidonoyl glycine-induced cell migration. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 22834922
  14. Δ(9) -Tetrahydrocannabinol and N-arachidonyl glycine are full agonists at GPR18 receptors and induce migration in human endometrial HEC-1B cells. cell or laboratory study; mechanism-focused research / 1 linked research note PubMed 21595653
  15. N-Acyl Amino Acids (Elmiric Acids): Endogenous Signaling Molecules with Therapeutic Potential. narrative or expert review; evidence still limited / 1 linked research note PubMed 29138268
  16. A GPR18-based signalling system regulates IOP in murine eye. animal study; mechanism-focused research / 1 linked research note PubMed 23461720
  17. The novel endocannabinoid receptor GPR18 is expressed in the rostral ventrolateral medulla and exerts tonic restraining influence on blood pressure. animal study; mechanism-focused research / 1 linked research note PubMed 24431468
  18. The elmiric acids: biologically active anandamide analogs. narrative or expert review; evidence still limited / 1 linked research note PubMed 18187165
  19. Cannabinoid and lipid-mediated vasorelaxation in retinal microvasculature. animal study; mechanism-focused research / 1 linked research note PubMed 24751709