Breast tissue and the endocannabinoid system
Mammary gland development.
Mammary gland development. Where the cannabinoid receptors CB1 and CB2 sit in this region, what they do there, and what is actually known about CBD; at three levels for Everyone, Students and Experts, with sources.
ChestCB1 high · CB2 very low (Human Protein Atlas)Last updated:
What's on this page?
Interactive 3D · real anatomy and real data
Where in your body are the cannabinoid receptors?
About 1.4 MB to download.
Regions
How to read it Choose a region, or tap a glowing point on the map.
- Solid light is the CB1 receptor, a ring is CB2. Each region has its own color; the color only tells regions apart.
- The strength of the light is the receptor gene level measured in human tissue (Human Protein Atlas). That is why the liver’s point is dim: a healthy liver has few receptors.
- With the layer selector above you can also see other receptors, the enzymes that make and break down endocannabinoids, and the liver enzymes that break down CBD and THC.
- Every piece of information shows its source and the type of evidence (human, animal, cell). You can change the reading level above.
- Drag to rotate. Use the + and − buttons to zoom; on a computer, Ctrl or ⌘ with the scroll wheel, on a phone, two fingers.
Breast: RNA level of the receptor gene in human tissue (tissue consensus data). CB1 RNA is high; CB2 was not measured. Human Protein AtlasHuman tissue
| Receptor | Gene | RNA (nTPM) | Level |
|---|---|---|---|
| CB1 | CNR1 | 14.1 | high |
| CB2 | CNR2 | 0 | very low |
What does it do there?
CB1 receptor RNA is measured at high levels in breast tissue; CB2 RNA is too low to measure. According to a review, CB1 and CB2 are found in the mammary gland. The mammary gland develops largely in adulthood; in one laboratory study, the endocannabinoid-degrading enzyme FAAH turned out to be important in this development: by adjusting anandamide levels and the CB1 activation that depends on them, it guided the differentiation of gland cells. Human Protein AtlasHuman tissueElgueta 2026ReviewTundidor 2024AnimalHuman tissueCell / lab
Endocannabinoids are also found in breast milk. In one study, 12 of the 13 endocannabinoids and related compounds measured were detected in milk; the most abundant was 2-AG. A fatty acid the mother gets from food (DHA) was linked to the endocannabinoid derived from it in milk. Wu 2016Human tissueGaitán 2018Human tissueGaitán 2021Human tissue
Student level: terms and cell types
According to a review, CB1 and CB2 are expressed in the mammary gland, and endocannabinoids are also present in breast milk. Mammary gland development occurs largely in adulthood. The endocannabinoid-degrading enzyme FAAH was required for luminal lineage specification in the mammary gland and, by controlling anandamide levels and thus CB1 activation, supported the hormone-driven secretory differentiation of mammary epithelial cells. Human Protein AtlasHuman tissueElgueta 2026ReviewTundidor 2024AnimalHuman tissueCell / lab
Liquid chromatography–tandem mass spectrometry detected 12 of 13 endocannabinoids and related compounds (2–111 nM) in human milk, with the highest levels for 2-AG; most concentrations depended on storage conditions. In transitional and mature milk from 24 mothers, 12 compounds were identified, including anandamide, 2-AG, PEA and OEA. Among the endocannabinoids, dietary DHA was associated only with docosahexaenoyl glycerol (DHG). Wu 2016Human tissueGaitán 2018Human tissueGaitán 2021Human tissue
Expert level: method notes and numbers
Breast: RNA level of the receptor gene in human tissue (tissue consensus data). CB1 RNA is high; CB2 was not measured. Human Protein AtlasHuman tissue
Method note
HPA tissue consensus data (HPA and GTEx samples combined), CNR1 14.1 nTPM. Tundidor 2024: human mammary epithelial cell datasets, FAAH immunofluorescence in surgical samples, FAAH−/− mice and differentiation in culture; evidence type taken from the full text (the PubMed record has no MeSH terms). Wu 2016: LC-MS/MS, number of participants not given in the abstract. Gaitán 2018 and 2021: n = 24 breastfeeding women. Human Protein AtlasHuman tissueTundidor 2024AnimalHuman tissueCell / labWu 2016Human tissueGaitán 2018Human tissueGaitán 2021Human tissue
The model is sex-neutral; breast tissue is not drawn as a separate part, and the chest area glows locally instead.
What is known about CBD?
There is no verified CBD finding or guide topic specific to this region.
Which receptor and enzyme genes are read in this region?
Values in this region for the genes in the map's layer selector: besides CB1 and CB2, the other targets of cannabinoids, the enzymes that make and break down endocannabinoids, and the liver enzymes that break down CBD and THC.
| Gene | What does it do? | Here | Tissue where it is read the most |
|---|---|---|---|
| Receptors | |||
| CB1 CNR1 | Cannabinoid receptor | 14.1 | cerebral cortex (18.6) |
| CB2 CNR2 | Cannabinoid receptor | 0.0 | spleen (8.4) |
| TRPV1 | Heat and chili pepper sensor · ion channel | 5.3 | liver (21.8) |
| GPR55 | Long an "orphan" receptor · in the cell membrane | 0.5 | testis (4.4) |
| PPARγ PPARG | Gene switch · in the cell nucleus | 83.9 | adipose tissue (153.2) |
| 5-HT1A HTR1A | Serotonin receptor · in the cell membrane | 0.0 | hippocampal formation (6.1) |
| TRPV2 | Relative of TRPV1 · ion channel | 10.1 | lung (29.5) |
| Endocannabinoid enzymes | |||
| NAPE-PLD NAPEPLD | Makes anandamide | 1.6 | kidney (13.9) |
| FAAH | Breaks down anandamide | 9.4 | testis (46.0) |
| DAGLα DAGLA | Makes 2-AG | 2.0 | cerebral cortex (12.3) |
| DAGLβ DAGLB | Makes 2-AG | 6.4 | adrenal gland (15.2) |
| MGL MGLL | Breaks down 2-AG | 89.3 | adipose tissue (161.3) |
| ABHD6 | Breaks down 2-AG | 9.3 | liver (60.7) |
| ABHD12 | Breaks down 2-AG | 27.4 | epididymis (125.2) |
| Enzymes that break down CBD and THC | |||
| CYP3A4 | Breaks down CBD and THC | 0.2 | liver (3,367.1) |
| CYP2C19 | Breaks down CBD | 0.0 | liver (178.0) |
| CYP2C9 | Breaks down THC | 0.1 | liver (1,607.6) |
RNA level shows how much the gene is read in this tissue; it does not directly show the amount of protein or how active an enzyme is. Human Protein Atlas (layers)Human tissue
Identifiers and citation
- Breast tissue
- Breast · MeSH D001940
- Receptors
- CB1 (CNR1, UniProt P21554) · CB2 (CNR2, UniProt P34972)
How to cite: cbd.school editorial team. Breast tissue and the endocannabinoid system. Endocannabinoid system 3D map, cbd.school. Last updated October 24, 2026. https://cbd.school/learn/endocannabinoid-system-map/meme/
The body model is derived from BodyParts3D (DBCLS, CC BY 4.0) and Z-Anatomy (CC BY-SA 4.0); receptor levels from Human Protein Atlas v25 (CC BY 4.0). The map, text and downloaded images are CC BY-SA 4.0. An independent expert review has not been done yet. All licenses
Other pages of the map
Overview: what the endocannabinoid system is, the feedback brake at the synapse, CBD's targets, lesson mode, data and licenses.
Sources
Show 7 references
- Human Protein Atlas v25: tissue RNA consensus data (rna_tissue_consensus.tsv, HPA and GTEx, nTPM) and brain region data (rna_brain_region_hpa.tsv, nTPM), CNR1 (ENSG00000118432) and CNR2 (ENSG00000188822); v25.proteinatlas.org, file date November 6, 2025, downloaded October 24, 2026. Uhlén M et al. Tissue-based map of the human proteome. Science. 2015;347(6220):1260419. License CC BY 4.0. PMID 25613900 · doi:10.1126/science.1260419 Human tissue
- Elgueta S, Sánchez N, Valdivia P, Contreras-Duarte S. Exploring the Endocannabinoid System's Influence on Mammary Tissue and Breast Milk Inflammation in Maternal Chronic Obesity. Biomolecules. 2026;16(2):201. PMID 41750272 · doi:10.3390/biom16020201 Review
- Tundidor I, Seijo-Vila M, Blasco-Benito S et al. Fatty acid amide hydrolase drives adult mammary gland development by promoting luminal cell differentiation. Cell Death Discov. 2024;10(1):12. PMID 38184644 · doi:10.1038/s41420-023-01788-1 AnimalHuman tissueCell / lab
- Wu J, Gouveia-Figueira S, Domellöf M et al. Oxylipins, endocannabinoids, and related compounds in human milk: Levels and effects of storage conditions. Prostaglandins Other Lipid Mediat. 2016;122:28-36. PMID 26656029 · doi:10.1016/j.prostaglandins.2015.11.002 Human tissue
- Gaitán AV, Wood JT, Zhang F et al. Endocannabinoid Metabolome Characterization of Transitional and Mature Human Milk. Nutrients. 2018;10(9):1294. PMID 30213124 · doi:10.3390/nu10091294 Human tissue
- Gaitán AV, Wood JT, Liu Y et al. Maternal Dietary Fatty Acids and Their Relationship to Derived Endocannabinoids in Human Milk. J Hum Lact. 2021;37(4):813-820. PMID 33656382 · doi:10.1177/0890334421993468 Human tissue
- Human Protein Atlas v25: tissue RNA consensus data (rna_tissue_consensus.tsv, HPA and GTEx, nTPM), the 17 genes in the map's layer selector: CNR1, CNR2, TRPV1, GPR55, PPARG, HTR1A, TRPV2, NAPEPLD, FAAH, DAGLA, DAGLB, MGLL, ABHD6, ABHD12, CYP3A4, CYP2C19, CYP2C9; v25.proteinatlas.org/download/tsv/rna_tissue_consensus.tsv.zip, downloaded October 24, 2026. Uhlén M et al. Tissue-based map of the human proteome. Science. 2015;347(6220):1260419. License CC BY 4.0. PMID 25613900 · doi:10.1126/science.1260419 Human tissue