Treatment with Sutherlandia frutescens ssp. microphylla alters the corticosterone response to chronic intermittent immobilization stress in rats
Much anecdotal evidence suggests a stress-relieving effect of the Sutherlandia frutescens herb. We investigated this in a model of chronic intermittent immobilization stress in 40 adult male Wistar rats. A warm water extract of Sutherlandia leaves (4 mg/ml) was used as treatment and isotonic saline as placebo, both injected intraperitoneally. The four experimental groups were: a) control + treatment (CS); b) control + placebo (CP); c) immobilization + treatment (IS) and d) immobilization + placebo (IP). After 28 days, resting blood corticosterone, testosterone, interleukin (IL)-6 and tumor necrosis factor (TNF)-α concentrations were measured. Data were analysed with two-way ANOVA. Immobilization stress resulted in significantly increased corticosterone concentrations in IP vs CP (81 ± 11 vs 22 ±7 ng/ml, P < 0.001), whereas corticosterone concentrations were significantly decreased in IS (43 ± 14 ng/ml, P < 0.05) compared to IP. The two Sutherlandia-treated groups did not differ (CS 57 ± 11 ng/ml). Neither testosterone nor IL-6 and TNF-α concentrations were significantly different among groups. In summary, our data show that Sutherlandia frutescens treatment effectively decreased the corticosterone response to chronic stress, thereby scientifically confirming the indigenous wisdom.