Rearing rats in isolation has been shown to produce behavioral and neurochemical alterations similar to those observed in psychoses such as schizophrenia. Also, a dysregulation in both the endocannabinoid and dopaminergic systems has been implicated in schizophrenia. The aim of this study was to determine if there are differences in CB 1 receptor and fatty acid amide hydrolase (FAAH) protein expression, as well as D 2 dopamine receptor expression in different brain regions in rats reared in different environmental conditions. Twenty-one day old male Sprague-Dawley rats were either reared in individual cages (isolated rats) or in group cages of 6 per cage (group housed rats) for 8 weeks. Quantitative fluorescence immunohistochemistry was performed on brain slices using antibodies specific to the CB 1 or D 2 receptor, or the enzyme FAAH. Raising rats in isolation led to a significant decrease in CB 1 receptor expression in the caudate putamen and the amygdala, a significant increase in FAAH expression in the caudate putamen and the nucleus accumbens core and shell, and no significant change in D 2 receptor expression in any region studied. These results indicate that the endocannabinoid system is altered in an animal model of aspects of psychosis. This implies that rearing rats under different housing conditions may provide new insight into the role of the endocannabinoid system in the development of psychoses.