The
present study investigated the antidepressant-like effects of navel
orange [Citrus sinensis (L.) Osbeck]
essential oil (OEO) and its main components using the chronic unpredictable
mild stress (CUMS) model mice and explored its possible mechanisms.
The results indicated that OEO inhalation significantly ameliorated
the depression-like behaviors of CUMS mice with decreased body weight,
sucrose preference, curiosity, and mobility as well as shortened immobile
time and attenuated dyslipidemia. Limonene was the most abundant compound
in the sniffing OEO environment and mice brain after sniffing, and
it was not metabolized immediately in the brain. In addition, limonene
inhalation significantly restored CUMS-induced depressive behavior,
hyperactivity of hypothalamic–pituitary–adrenal axis,
and the decrease of monoamine neurotransmitter levels, with downregulation
of brain-derived neurotrophic factor and its receptor expression in
the hippocampus. Thus, the study indicates that the improvements in
neuroendocrine, neurotrophic, and monoaminergic systems are related
to the antidepressant effects of limonene.