CNR1 and obesity due to melanocortin 4 receptor deficiency: Subsequent cross of Cnr1f/f mice with cell-type-specific Cre-deleter mice [27] in several labs produced deletion of Cnr1 gene in principal neurons [24], glutamatergic or GABAergic neurons [28,29], noradrenergic neurons [30], dorsal root ganglia [31], astrocytes [32,33], adipocytes [34], podocytes [35], keratinocytes [36], and hepatocytes [37] that revealed CB1R cell-type-specific functions in extinguishing fear, epilepsy, osteoporosis, analgesia, learning and memory, obesity, diabetic nephropathy, inflammation, and hepatic steatosis, respectively.