Antidepressant- and anxiolytic-like activities of Rosmarinus officinalis extract in rodent models: Involvement of oxytocinergic system

Background: Oxytocin (OXT), a neuropeptide involved in mammal reproductive and prosocial behaviors, has been reported to interact with various stressor-provoked neurobiological changes, including neuroendocrine, neurotransmitter, and inflammatory processes. In view of disturbances in psychosocial relationships due to social isolation and physical distancing measures amid the COVID-19 pandemic, being one of the triggering factors for the recent rise in depression and anxiety, OXT is a potential candidate for a new antidepressant. Methods: In this present study, we have aimed to investigate the effects of oral administration of Rosmarinus officinalis extract (RE), extracted from distillation residue of rosemary essential oil, on central OXT level in the context of other stress biomarkers and neurotransmitter levels in mice models. Tail suspension test (TST) and elevated plus maze test (EPMT) following LPS injection were employed to assess depressive- and anxiety-like behavior in mice, respectively. Findings: Pretreatment with RE for seven days significantly improved behavior in TST and EPMT. Whole-genome microarray analysis reveals that RE significantly reversed TST stress-induced alterations in gene expressions related to oxytocinergic and neurotransmitter pathways and inflammatory processes. In both models, RE significantly increased central Oxt and Oxtr expressions, as well as OXT protein levels. RE also significantly attenuated stress-induced changes in serum corticosterone, brain and serum BDNF levels, and brain neurotransmitters levels in both models. Interpretation: Altogether, our study is the first to report antidepressant- and anxiolytic-like activities of RE through modulating oxytocinergic system in mice brain and thus highlights the prospects of RE in the treatment of depressive disorders of psychosocial nature.