Camellia euphlebia exerts its antidepressant-like effect via modulation of the hypothalamic-pituitary-adrenal axis and brain monoaminergic systems

Camellia euphlebia (family, Theaceae) is a Chinese folk medicine, known for its multiple pharmacological properties. The present study aimed to provide further insights into the therapeutic basis of C. euphlebia using several animal behavioral tests and physiological indexes. Tail suspension test, forced swimming test, open-field test, chronic unpredictable mild stress (CUMS), reversal of reserpine-induced hypothermia and palpebral ptosis, and 5-hydroxytryptophane-induced head-twitch response were used to evaluate the antidepressant effect of aqueous extract of Camellia euphlebia (AEC) on mice. The possible underlying mechanism was explored by investigating the changes associated with several parameters of animal behavior, as well as the changes in monoamine neurotransmitter and stress hormone levels in these animals during the tests. Mice administered AEC at 100 and 200 mg/kg/day doses for 7 days showed significantly reduced immobility duration in forced swimming test and tail suspension test, whilst exhibiting no apparent changes in locomotor activity. Additionally, administration of AEC also effectively antagonized reserpine-induced palpebral ptosis and hypothermia and enhanced 5-hydroxytryptophane-induced head-twitch response. AEC significantly elevated the levels of serotonin, noradrenaline and dopamine in the blood and brain compared to non-treated mice. After 28 days of administration, the maximum AEC dose (100 mg/kg/day) significantly reversed CUMS-induced inhibition of weight gain and sucrose intake, while decreasing the levels of plasma adrenocorticotropic hormone and serum corticosterone. The antidepressant effect of AEC appeared to involve the alteration of hypothalamic-pituitary-adrenal axis and monoaminergic systems.