Portulaca oleracea L. prevents lipopolysaccharide-induced passive avoidance learning and memory and TNF-α impairments in hippocampus of rat

There is a growing body of evidence that neuroinflammation can impair memory. It has been indicated that Portulaca oleracea Linn. (POL), possess anti-inflammatory activity and might improve memory disruption caused by inflammation. In this study the effect of pre-treatment with the hydro-alcoholic extract of POL on memory retrieval investigated in lipopolysaccharide (LPS) treated rats. Male Wistar rats (200-220 g) received either a control diet or a diet containing of POL (400 mg/kg, p.o.) for 14 days. Then, they received injections of either saline or LPS (1 mg/kg, i.p.). In all the experimental groups, 4 h following the last injection, passive avoidance learning (PAL) and memory test was performed. The retention test was done 24 h after the training and then the animals were sacrificed. Hippocampal TNF-α levels measured using ELISA as one criteria of LPS-induced neuroinflammation. The results indicated that LPS significantly impaired PAL and memory and increased TNF-α levels in hippocampus tissue. Pre-treatment with POL improved memory in control rats and prevented memory and TNF-α deterioration in LPS treated rats. Taken together, the results of this study suggest that the hydro-alcoholic extract of POL may improve memory deficits in LPS treated rats, possibly via inhibition of TNF-α and anti-inflammatory activity.