Abstract: Objective：To investigate the protective effects and potential mechanisms of Dendrobium nobile polysaccharides （DNP） from Dendrobium nobile Lindl. on learning and memory deficits induced by lipopolysaccharide （LPS）. Methods：Rats were orally treated with DNP（ 40，80，160 mg·kg-1） for 7 days，followed by bilateral intra-cerebroventricular injection of LPS （20 μg·rat-1） to induce learning and memory deficits. Rats were continued to receive DNP until the end of experiments. Morris water maze was used to test the abilities of spatial learning and memory. The neuronal injury in hippocampus was observed by hematoxylin-eosin staining. The mRNA and protein expressions of neuroinflammation-related genes and proteins in rats hippocampus were detected by real time RT-PCR and Western blot，respectively. Results：Compared to sham （saline-injected） rats，LPS significantly prolonged the escape latency in the navigation test and shortened the adjusted escape latency （P<0.01）. These learning and memory deficits were significantly improved by DNP treatment （P<0.01）. LPS injection caused neuronal injury in hippocampus，and increased the mRNA and protein expressions of TNF-α，IL-1β and TGF-β1 in rat hippocampus （P<0.01），which were suppressed by DNP treatments （P<0.05）. Conclusions：DNP could protect LPS-induced learning and memory deficits and neuronal injury in rats. The mechanisms appear to be due to the inhibition of LPS-elicited inflammatory responses in the hippocampus.

Key words: Dendrobium nobile （Dendrobium nobile Lindl.） polysaccharides（DNP）, lipopolysaccharide, learning and memory, inflammatory factor