Abstract

Cannabinoid receptor type 1 (CB1R) is the most abundant cannabinoid receptor in central nervous system. Clinical studies and animal models have shown that the attenuation of endocannabinoid system signaling correlates with the development of psychiatric disorders such as anxiety, depression and schizophrenia. In the present work, multiple behavioral tests were performed to evaluate behaviors related to anxiety and depression in CB1R+/- and CB1R-/-. CB1R+/- mice had anxiety-related behavior similar to wild type (CB1R+/+) mice, whereas CB1R-/- mice displayed an anxious-like phenotype, which indicates that lower expression of CB1R is sufficient to maintain the neural circuits modulating anxiety. In addition, CB1R-/- mice exhibited alterations in risk assessment and less exploration, locomotion, grooming, body weight and appetite. These phenotypic characteristics observed in CB1R-/- mice could be associated with symptoms observed in human psychiatric disorders such as depression. A better knowledge of the neuromodulatory role of CB1R may contribute to understand scope and limitations of the development of medical treatments.