Clinical studies show higher levels of cannabinoid CB1 receptors (CB1R) in the brain of schizophrenic patients while preclinical studies report a significant functional interaction between dopamine D2 receptors and CB1Rs as well as an upregulation of CB1Rs after antipsychotic treatment. These findings prompted us to study the effects of chronic oral intake of a first and a second generation antipsychotic, haloperidol and olanzapine, on the levels and distribution of CB1Rs in the rat brain. Rats consumed either regular chow or high-fat food and drank water, haloperidol drinking solution (1.5mg/kg), or olanzapine drinking solution (10mg/kg) for four weeks. Motor and cognitive functions were tested at the end of treatment week 3 and upon drug discontinuation. Two days after drug discontinuation, rats were euthanized and brains were processed for in vitro receptor autoradiography. In chow-fed animals, haloperidol and olanzapine increased CB1R levels in the basal ganglia and the hippocampus, in a similar, but not identical pattern. In addition, olanzapine had unique effects in CB1R upregulation in higher order cognitive areas, in the secondary somatosensory cortex, in the visual and auditory cortices and the geniculate nuclei, as well as in the hypothalamus. High fat food consumption prevented antipsychotic-induced increase in CB1R levels in all regions examined, with one exception, the globus pallidus, in which they were higher in haloperidol-treated rats. The results point towards the hypothesis that increased CB1R levels could be a confounding effect of antipsychotic medication in schizophrenia that is circumveneted by high fat feeding.
Keywords: Antipsychotic; CB1; High fat diet.
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