Endocannabinoid 2-Arachidonoylglycerol Levels in the Anterior Cingulate Cortex, Caudate Putamen, Nucleus Accumbens, and Piriform Cortex Were Upregulated by Chronic Restraint Stress

Endocannabinoid 2-arachidonoylglycerol (2-AG) has been implicated in habituation to stress, and its augmentation reduces stress-induced anxiety-like behavior. Chronic restraint stress (CRS) changes the 2-AG levels in some gross brain areas, such as the forebrain. However, the detailed spatial distribution of 2-AG and its changes by CRS in stress processing-related anatomical structures such as the anterior cingulate cortex (ACC), caudate putamen (CP), nucleus accumbens (NAc), and piriform cortex (PIR) are still unclear. In this study, mice were restrained for 30 min in a 50 mL-centrifuge tube for eight consecutive days, followed by imaging of the coronal brain sections of control and stressed mice using desorption electrospray ionization mass spectrometry imaging (DESI-MSI). The results showed that from the forebrain to the cerebellum, 2-AG levels were highest in the hypothalamus and lowest in the hippocampal region. 2-AG levels were significantly (p < 0.05) upregulated and 2-AG precursors levels were significantly (p < 0.05) downregulated in the ACC, CP, NAc, and PIR of stressed mice compared with control mice. This study provided direct evidence of 2-AG expression and changes, suggesting that 2-AG levels are increased in the ACC CP, NAc, and PIR when individuals are under chronic stress.