In the caudate putamen, social isolation increased cannabinoid receptor densities relative to group rearing. Likewise, cannabinoid receptor densities were increased in the caudate putamen in a model of schizophrenia induced by neonatal basolateral amygdala lesions (Bouwmeester et al., 2007). However, Malone and colleagues (2008) recently reported decreases in CB1 immunoreactivity in the caudate putamen of socially-isolated rats using immunohistochemical methods. Several explanations may account for the discrepancy between our study and that of Malone et al. (2008). First, differences in techniques used to measure receptors (immunofluorescence vs. binding density) exist between the two studies. In our work, [3H]CP55,940 binding would be expected to label all populations of cannabinoid receptors, whereas the C-terminal antibody used by Malone et al. (2008) may preferentially label specific subpopulations of cannabinoid receptors. Malone et al. (2008) used a CB1 antibody, raised in goat, that was directed against residues 401 – 473 of the C-terminal of CB1. This antibody is thought to preferentially label CB1 receptors on GABAergic, but not glutamatergic, neurons (Katona et al., 2006, Kawamura et al., 2006, Nyilas et al., 2009). By contrast,
