Pharmacological Evaluation of Cannabinoid Receptor Modulators Using GRAB Sensor.

Cannabinoid receptors CBR and CBR are G-protein coupled receptors acted upon by endocannabinoids (eCBs), namely 2-arachidonoylglycerol (2-AG) and -arachidonoyl ethanolamine (AEA), with unique pharmacology and modulate disparate physiological processes. A genetically encoded GPCR activation-based sensor that was developed recently-GRAB-has been shown to be capable of monitoring real-time changes in eCB levels in cultured cells and preclinical models. However, its responsiveness to exogenous synthetic cannabinoid agents, particularly antagonists and allosteric modulators, has not been extensively characterized. This current study expands upon the pharmacological characteristics of GRAB to enhance the understanding of fluorescent signal alterations in response to various functionally indiscriminate cannabinoid ligands. The results from this study could enhance the utility of the GRAB sensor for in vitro as well as in vivo studies of cannabinoid action and may aid in the development of novel ligands.