Trans-cinnamaldehyde shows anti-depression effect in the forced swimming test and possible involvement of the endocannabinoid system.

Depression is a mental disease that significantly reduces the quality of patients' life. Around 322 million people of all ages carry the heavy burden of depression on a worldwide scale, with a life-time prevalence of 20% according to the WHO. Trans-cinnamaldehyde (TCA) is an excellent COX-2 inhibitor in central nervous system which is a main constituent of GUIZHI as a member of traditional Chinese herb. Furthermore, previous studies demonstrated that TCA suppressed depression-like behavior in chronic unexpected mild stress, plus maze test and open field test. However, the molecular mechanism of TCA anti-depression effect is not clear. We examined the immobility of TCA pretreated male BALB/c mice in the forced swimming test (FST). Results show that TCA (50 mg/kg, po) revealed a significant effect on reduced immobility in the FST, compared with SAL group which indicated that TCA suppressed depression-like behavior. Moreover, TCA elevated the level of 5-HT and decreased the ratio of Glu/GABA in mice hippocampus. Compared with SAL + FST group, TCA + FST group significantly decreased COX-2, TRPV1 and CB1 protein level in mice hippocampus (p < 0.05, p < 0.05, p < 0.01). These findings suggest that TCA treatment exerted anti-depressive effect and was able to regulate neurotransmitters in the FST. This effect may have positive influence on the endocannabinoid (eCB) system.