Recent advances in the development of CB₁R selective probes

Cannabinoid subtype 1 receptors (CB₁Rs) are an important class of G protein-coupled receptors (GPCRs) belonging to the endocannabinoid system. CB₁Rs play a crucial modulatory role in the functioning of other neurotransmitter systems and are involved in a wide range of physiological functions and dysfunctions; thus, they are considered one of the most important targets for drug development, as well as diagnostic purposes. Despite this, only a few molecules targeting this receptor are available on the pharmaceutical market, thus emphasizing the need to gain a deeper understanding of the complex activation pathways of CB₁Rs and how they regulate diseases. As part of this review, we provide an overview of pharmacological and imaging tools useful for detecting CB₁Rs. Herein, we summarize the derivations of cannabinoids and terpenoids with fluorescent compounds, radiotracers, or photochromic motifs. CB₁Rs’ molecular probes may be used in vitro and, in some cases, in vivo for investigating and exploring the roles of CB₁Rs together with the starting point for the development of CB₁R-targeted drugs.