The effects of Sceletium tortuosum in an in vivo model of psychological stress

Aim of the study: Sceletium, and especially Sceletium tortuosum, is traditionally used as masticator and thought to have a sedative effect which may be beneficial to reduce symptoms of anxiety and/or depression. The current study evaluated the scientific merit of these anecdotal claims in an in vivo model of psychological stress. Materials and methods: Male Wistar rats were administered either placebo, 5 or 20 mg/kg/day of Sceletium tortuosum extract for 17 days by daily oral gavage. 50% of rats were exposed to repeated restraint stress lasting 1 h for the last 3 days of treatment. Rat behavioral changes in response to stress were assessed using the elevated plus maze on the last day of restraint, immediately after the restraint session. Rats were sacrificed 24 h after the last restraint exposure and whole blood collected. Results: Behavior indicated a limited effect of lower dose Sceletium to decrease restraint stress-induced self-soothing behavior, as well as to decrease stress-induced corticosterone levels. However, increased IL-1 beta levels argue against the claim that the plant may act as selective serotonin reuptake inhibitor, while this result combined with increased levels of C-reactive protein and prostaglandin E-2 suggest intolerance to the treatment. Decreased IL-2 and increased IL-10 levels in response to Sceletium treatment suggest a suppressive effect on T helper 1 immune function. Conclusions: Although data indicates a limited positive effect of Sceletium on restraint-induced anxiety, numerous side-effects were evident. More research is required to derive an optimal therapeutic dose. (C) 2010 Elsevier Ireland Ltd. All rights reserved.