CB1 is the primary brain receptor activated by marijuana. It is down-regulated in the brain in response to delta-9-tetrahydrocannabinol (Breivogel et al., 1999; Romero, Berrendero, Garcia-Gil, Ramos, & Fernandez-Ruiz, 1998), the psychoactive component within marijuana. CB1 is a member of the Gi/Go-protein-coupled receptor superfamily (Pertwee, 1997). Its activation triggers a diverse range of cellular responses, including multiple second messenger transduction mechanisms important in regulating dopaminergic and GABAergic neurons (Eggan & Lewis, 2007; Gardner, 2005; Laviolette & Grace, 2006; Lewis & Hashimoto, 2007; Price et al., 2007). CB1 is widely expressed in the dorsolateral prefrontal cortex, hippocampus, thalamus and cerebellum (Pazos et al., 2005); which are also brain regions implicated in the pathophysiology of schizophrenia (Lewis & Gonzalez-Burgos, 2008) and in addiction/reward circuitry (Haber & Knutson, 2009). CB1 receptors are localized predominantly in neurons with the highest concentrations in afferent axon terminals, neuronal cell bodies, and dendrites (Ong & Mackie, 1999). However, recent studies have found CB1 in oligodendrocytes (Moldrich & Wenger, 2000; Rodriguez, Mackie, & Pickel, 2001) as well as in oligodendrocyte progenitor cells within the subventricular zones where post-natal
