Repeated cannabidiol treatment affects neuroplasticity and endocannabinoid signaling in the prefrontal cortex of the Flinders Sensitive Line (FSL) rat model of depression

Delayed therapeutic responses and limited efficacy are the main challenges of existing antidepressant drugs, thereby incentivizing the search for new potential treatments. Cannabidiol (CBD), non-psychotomimetic component of cannabis, has shown promising antidepressant effects in different rodent models, but its mechanism of action remains unclear. Herein, we investigated the antidepressant-like effects of repeated CBD treatment on behavior, neuroplasticity markers and lipidomic profile in the prefrontal cortex (PFC) of Flinders Sensitive Line (FSL), a genetic animal model of depression, and their control counterparts Flinders Resistant Line (FRL) rats. Male FSL animals were treated with CBD (10 mg/kg; i.p.) or vehicle (7 days) followed by Open Field Test (OFT) and the Forced Swimming Test (FST). The PFC was analyzed by a) western blotting to assess markers of synaptic plasticity and cannabinoid signaling in synaptosome and cytosolic fractions; b) mass spectrometry-based lipidomics to investigate endocannabinoid levels (eCB). CBD attenuated the increased immobility observed in FSL, compared to FRL in FST, without changing the locomotor behavior in the OFT. In synaptosomes, CBD increased ERK1, mGluR5, and Synaptophysin, but failed to reverse the reduced CB1 and CB2 levels in FSL rats. In the cytosolic fraction, CBD increased ERK2 and decreased mGluR5 expression in FSL rats. Surprisingly, there were no significant changes in eCB levels in response to CBD treatment. These findings suggest that CBD effects in FSL animals are associated with changes in synaptic plasticity markers involving mGluR5, ERK1, ERK2, and synaptophysin signaling in the PFC, without increasing the levels of endocannabinoids in this brain region.

Cannabidiol attenuates behavioral changes in a rodent model of schizophrenia through 5-HT1A, but not CB1 and CB2 receptors

Preclinical and clinical data indicate that cannabidiol (CBD), a non-psychotomimetic compound from the Cannabis sativa plant, can induce antipsychotic-like effects. In an animal model of schizophrenia based on the antagonism of NMDA receptors, the behavioral and molecular changes induced by repeated treatment with the NMDA receptor antagonist MK-801 were prevented when CBD was co-administered with MK-801. It is unknown, however, if CBD would reverse these changes once they have been established. Thus, in the present study we used male C57BL/6J mice, 6 weeks old, to evaluate whether daily CBD injection for seven days, starting after the end of the repeated treatment with MK-801 for 14 days, would reverse MK-801-induced deficits in the social interaction (SI) and novel object recognition (NOR) tests, which have been used to investigate the negative and cognitive symptoms of schizophrenia, respectively. We also assessed whether CBD effects would be blocked by pretreatment with AM251, a CB1 receptor antagonist, AM630, a CB2 receptor antagonist, or WAY100635, a 5-HT1A receptor antagonist. CBD and the second-generation antipsychotic clozapine, used as a positive control, attenuated the impairments in the SI and NOR tests induced by repeated administered MK-801. CBD effects were blocked by WAY100635, but not by AM251 or AM630. These data suggest that CBD induces antipsychotic-like effects by activating 5-HT1A receptors and indicate that this compound could be an interesting alternative for the treatment of negative and cognitive symptoms of schizophrenia.