Neurodevelopmental Gene Expression of Cannabinoid Receptor 2 (CB2R) in C57Bl/6J and BTBRT+tf/J and the CB2R Expression in Transgenic knockout mice (MUBx, DAT, DATCI, SERT)

The endocannabinoid system (ECS) consists of receptors, ligands, and the enzymes that degrade them. Two G‐protein coupled receptors that have been identified, cannabinoid receptors 1 and 2 (CB1R and CB2R). CB1R was discovered first and has been extensively studied. It has been shown to regulate the stress response through the HPA‐axis and also has been implicated in addiction. CB2R has been shown to play a role in embryo neurodevelopment and growth. It was recently discovered that CB1R is expressed in macrophages, microglial cells, and also on neurons. CB2R has been implicated in a number of brain disorders, but its function and role in the brain is not fully understood. Part of the controversy is due the fact that CB2R is induced during inflammation. Previous studies done in our lab with whole brains showed that the autism spectrum BTBRT+tf/J mice expressed more CB2R than the wild type C57bl/6J. This experiment sought to establish a baseline for the CB2R expression in the brain at various stages in their development (D0, D7, D14, D21, D35 and D42). Brains were dissected into three main parts; the prefrontal cortex (PFC), the cerebellum (CER) and the remainder of the brain designated as the mid brain (MID). RNA was extracted from these brain samples, converted to cDNA and then using RT‐PCR the CB2R gene expression was determined using the delta‐delta CT method. Transgenic mice strains were used for the second part of this study were dopamine transporter knockout (DAT), Serotonin transporter knockout (SERT), Mu‐Opioid receptor knockout (MUBx) and the Dopamine transporter knockout cocaine insensitive (DAT‐CI). Comparisons were made between the wild type and mutants of the knockout species. However the DAT mutant and heterozygous were compared because the mutant species do not survive. The results show differences in the expression of the CB2R at different stages in development and also in the dissected brain parts. Overall the BTBR mice had more CB2R gene expression than the wild type C57. These results were consistent with whole brain studies. The transgenic study showed different levels of CB2R expression between the strains. The different expression levels in the transgenic mice indicate a possible interaction between the CB2R and the knockout pathways. Based on these results conditional knockout species are being bred for further research. Support or Funding Information NIH grant DA032890