ABSTRACT
The amygdala is an important hub for regulating emotions and is involved in the pathophysiology of many mental diseases, such as depression and anxiety. Meanwhile, the endocannabinoid system plays a crucial role in regulating emotions and mainly functions through the cannabinoid type-1 receptor (CB1R), which is strongly expressed in the amygdala of non-human primates (NHPs). However, it remains largely unknown how the CB1Rs in the amygdala of NHPs regulate mental diseases. Here, we investigated the role of CB1R by knocking down the cannabinoid receptor 1 (CNR1) gene encoding CB1R in the amygdala of adult marmosets through regional delivery of AAV-SaCas9-gRNA. We found that CB1R knockdown in the amygdala induced anxiety-like behaviors, including disrupted night sleep, agitated psychomotor activity in new environments, and reduced social desire. Moreover, marmosets with CB1R-knockdown had up-regulated plasma cortisol levels. These results indicate that the knockdown of CB1Rs in the amygdala induces anxiety-like behaviors in marmosets, and this may be the mechanism underlying the regulation of anxiety by CB1Rs in the amygdala of NHPs.
Subject(s)
Animals , Callithrix , Receptors, Cannabinoid , Anxiety , Amygdala , Cannabinoids , PhenotypeABSTRACT
Cannabinoid receptors are one of the most expressed G protein-coupled receptors in the central nervous system, which are potential drug targets for inflammation, pain and drug abuse. Cannabinoid receptors are composed of type 1 receptor (CB1R), type 2 receptor (CB2R) and other receptors, of which CB1R plays a vital role in regulating central memory, cognition, and motor function. Therefore, screening CB1R agonists has potential value in treating nervous system diseases. In this study, the intracellular loop 3 (ICL3) domain of CB1R was replaced with a circular-permutated enhanced green fluorescent protein (cpEGFP). After infecting HEK 293T cells with lentivirus particles, we obtained a stable cell line that was overexpressed human CB1R-cpEGFP after puromycin selection. The interaction between receptor agonists and CB1R led to the change of receptor conformation, resulting in de-protonation of the EGFP, and enhancing the fluorescence intensity. Therefore, active CB1R compounds could be verified by measuring the fluorescence intensity. Using CB1R agonist arachidonyl-2′-chloroethylamide (ACEA) as a positive control to evaluate the reliability of this model, studies have shown that ACEA could induce receptor activation and increase fluorescence intensity, while antagonist rimonabant inhibited receptor activation with unchanged fluorescence intensity. In conclusion, this study successfully constructed a fluorescent probe screening model for CB1R agonists.
ABSTRACT
Cannabinoid type 1 receptor (CB1R), as the major member of the endocannabinoid system, is among the most abundant receptors expressed in the central nervous system. CB1R is mainly located on the axon terminals of presynaptic neurons and participate in the modulation of neuronal excitability and synaptic plasticity, playing an important role in the pathogenesis of various neuropsychiatric diseases. In recent years, the consistent development of CB1R radioligands and the maturity of molecular imaging techniques, particularly positron emission tomography (PET) may help to visualize the expression and distribution of CB1R in central nervous system . At present, CB1R PET imaging can effectively evaluate the changes of CB1R levels in neuropsychiatric diseases such as Huntington's disease and schizophrenia, and its correlation with the disease severity, therefore providing new insights for the diagnosis and treatment of neuropsychiatric diseases. This article reviews the application of CB1R PET imaging in Alzheimer's disease, Parkinson's disease, Huntington's disease, schizophrenia, post-traumatic stress disorder, cannabis use disorder and depression.