The striatum may be a unique region where isolation rearing alters D2 and CB1 receptor monomer expression (Bean and Lee, 1991, Malone et al., 2008, King et al., 2009). In striatal membranes, antagonistic intramembrane interaction occurred whereby CB1 receptor stimulation reduced D2 receptor affinity (Marcellino et al., 2008). Increases in CB1 receptor densities in isolates may produce altered D2 receptor dependent neurotransmission in the striatum. Given the presence of D2-CB1 receptor heterodimers in the striatum (for review see Ferre et al., 2009), social isolation may also alter D2-CB1 receptor heterodimer expression. At present, no selective pharmacological agent for a D2-CB1 receptor heterodimer is commercially available to directly test this hypothesis. Notwithstanding, future studies could extend the work of Malone et al. (2008) to obtain a description of D2-CB1 receptor colocalization after social isolation.
