GABA_Areceptors are the major ionotropic inhibitory neurotransmitter receptors. The endocannabinoid system is a lipid signaling network that modulates different brain functions. Here we show a direct molecular interaction between the two systems. The endocannabinoid 2-arachidonoyl glycerol (2-AG) potentiates GABA_Areceptors at low concentrations of GABA. Two residues of the receptor located in the transmembrane segment M4 of β₂confer 2-AG binding. 2-AG acts in a superadditive fashion with the neurosteroid 3α, 21-dihydroxy-5α-pregnan-20-one (THDOC) and modulates δ-subunit–containing receptors, known to be located extrasynaptically and to respond to neurosteroids. 2-AG inhibits motility in CB₁/CB₂cannabinoid receptor double-KO, whereas β₂-KO mice show hypermotility. The identification of a functional binding site for 2-AG in the GABA_Areceptor may have far-reaching consequences for the study of locomotion and sedation.

The α-hemoglobin-derived dodecapeptide RVD-hemopressin (RVDPVNFKLLSH) has been proposed to be an endogenous agonist for the cannabinoid receptor type 1 (CB₁). To study this peptide, we have raised mAbs against its C-terminal part. Using an immunoaffinity mass spectrometry approach, a whole family of N-terminally extended peptides in addition to RVD-Hpα were identified in rodent brain extracts and human and mouse plasma. We designated these peptides Pepcan-12 (RVDPVNFKLLSH) to Pepcan-23 (SALSDLHAHKLRVDPVNFKLLSH), referring to peptide length. The most abundant Pepcans found in the brain were tested for CB₁ receptor binding. In the classical radioligand displacement assay, Pepcan-12 was the most efficacious ligand but only partially displaced both [³H]CP55,940 and [³H]WIN55,212-2. The data were fitted with the allosteric ternary complex model, revealing a cooperativity factor value α < 1, thus indicating a negative allosteric modulation. Dissociation kinetic studies of [³H]CP55,940 in the absence and presence of Pepcan-12 confirmed these results by showing increased dissociation rate constants induced by Pepcan-12. A fluorescently labeled Pepcan-12 analog was synthesized to investigate the binding to CB₁ receptors. Competition binding studies revealed K_i values of several Pepcans in the nanomolar range. Accordingly, using competitive ELISA, we found low nanomolar concentrations of Pepcans in human plasma and ∼100 pmol/g in mouse brain. Surprisingly, Pepcan-12 exhibited potent negative allosteric modulation of the orthosteric agonist-induced cAMP accumulation, [³⁵S]GTPγS binding, and CB₁ receptor internalization. Pepcans are the first endogenous allosteric modulators identified for CB₁ receptors. Given their abundance in the brain, Pepcans could play an important physiological role in modulating endocannabinoid signaling.

The Concise Guide to Pharmacology 2025/26 marks the seventh edition in this series of biennial publications in the British Journal of Pharmacology. Presented in landscape format, the guide provides a comparative overview of the pharmacology of drug target families. The concise nature of the Concise Guide refers to the style of presentation, being clear, accessible, and well‐structured, rather than the scope of the content, which spans approximately 500 pages. The Concise Guide summarises the key pharmacological properties of around 1900 human drug targets, and nearly 7000 interactions, involving around 4400 ligands. While the content is a substantially condensed version of the more detailed information and links available at the www.guidetopharmacology.org website, the printed guide serves as a permanent, citable, point‐in‐time record, that remains stable despite ongoing updates to the online database. The full contents of this publication can be found at https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bph.70234 . The Concise Guides provide expert‐curated recommendations of ‘Gold Standard’ selective pharmacological tools, available either commercially or as donations, which enable the identification of individual drug targets or families of drug targets. While the Concise Guide offers a more streamlined overview, more comprehensive information, including detailed pharmacological profiles and links to multiple online databases, is available through the Guide to Pharmacology website. The 2025/26 edition of the Concise Guide is based on material current as of mid‐2025, and supersedes all previous editions, including the 2023/24 Guide, and earlier Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), and as such provides official IUPHAR classification and nomenclature for human drug targets, where applicable. Enzymes are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and transporters. Each section includes nomenclature guidance, concise summaries, information of the best available pharmacological tools, key references, and suggestions for further reading.

Despite extensive research on the trafficking of anandamide (AEA) across cell membranes, little is known about the membrane transport of other endocannabinoids, such as 2-arachidonoylglycerol (2-AG). Previous studies have provided data both in favor and against a cell membrane carrier-mediated transport of endocannabinoids, using different methodological approaches. Because AEA and 2-AG undergo rapid and almost complete intracellular hydrolysis, we employed a combination of radioligand assays and absolute quantification of cellular and extracellular endocannabinoid levels. In human U937 leukemia cells, 100 nm AEA and 1 μm 2-AG were taken up through a fast and saturable process, reaching a plateau after 5 min. Employing differential pharmacological blockage of endocannabinoid uptake, breakdown, and interaction with intracellular binding proteins, we show that eicosanoid endocannabinoids harboring an arachidonoyl chain compete for a common membrane target that regulates their transport, whereas other N-acylethanolamines did not interfere with AEA and 2-AG uptake. By combining fatty acid amide hydrolase or monoacyl glycerol lipase inhibitors with hydrolase-inactive concentrations of the AEA transport inhibitors UCM707 (1 μm) and OMDM-2 (5 μm), a functional synergism on cellular AEA and 2-AG uptake was observed. Intriguingly, structurally unrelated AEA uptake inhibitors also blocked the cellular release of AEA and 2-AG. We show, for the first time, that UCM707 and OMDM-2 inhibit the bidirectional movement of AEA and 2-AG across cell membranes. Our findings suggest that a putative endocannabinoid cell membrane transporter controls the cellular AEA and 2-AG trafficking and metabolism.

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders and is characterized by the loss of dopaminergic neurons in the substantia nigra (SN). Although the causes of PD are not understood, evidence suggests that its pathogenesis is associated with oxidative stress and inflammation. Recent studies have suggested a protective role of the cannabinoid signalling system in PD. β-caryophyllene (BCP) is a natural bicyclic sesquiterpene that is an agonist of the cannabinoid type 2 receptor (CB2R). Previous studies have suggested that BCP exerts prophylactic and/or curative effects against inflammatory bowel disease through its antioxidative and/or anti-inflammatory action. The present study describes the neuroprotective effects of BCP in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced murine model of PD, and we report the results of our investigation of its neuroprotective mechanism in neurons and glial cells. In the murine model, BCP pretreatment ameliorated motor dysfunction, protected against dopaminergic neuronal losses in the SN and striatum, and alleviated MPTP-induced glia activation. Additionally, BCP inhibited the levels of inflammatory cytokines in the nigrostriatal system. The observed neuroprotection and inhibited glia activation were reversed upon treatment with the CB2R selective antagonist AM630, confirming the involvement of the CB2R. These results indicate that BCP acts via multiple neuroprotective mechanisms in our murine model and suggest that BCP may be viewed as a potential treatment and/or preventative agent for PD.