OBJECTIVETo investigate effects of total paeony glucosides (TPGs) on the expressions of Toll receptors (TLR4) and interleukin-33 (IL-33) in the brain tissue of D-galactose-induced aging rats. METHODS; Fifty SD rats were randomly divided into 5 groups, i.e., the blank control group, the model group, the high dose TPG group, the middle dose TPG group, and the low dose TPG group, 10 in each group. Equal volume of normal saline was subcutaneously injected to rats in the blank control group, while 10% D-galactose was subcutaneously injected to rats in the rest groups at 0.125 mL/g, once a day for 8 successive weeks to induce the aging rat model. TPG was administered at 300 mg/kg, 150 mg/kg, and 75 mg/kg to rats in the high, middle, and low dose TPG groups while injecting D-galactose from the 5th week of model preparation, once daily for 4 successive weeks. Equal volume of normal saline was administered to rats in the blank control group and the model group, once daily. The capability for learning and memory was detected using Morris water. The mRNA expressions of TLR4 and IL-33 in the brain tissue were detected using ELISA.

RESULTSCompared with the blank control group, the capability for learning and memory decreased in the model group with statistical difference (P < 0.05). Compared with the model group, the capability for learning and memory was obviously improved in all the medicated groups in a dose-dependent manner, showing statistical difference (P < 0.05). Compared with the blank control group, mRNA expressions of TLR4 and IL-33 in the brain tissue obviously increased after medication in the model group, showing statistical difference (P < 0.05). Compared with the model group, mRNA expressions of TLR4 and IL-33 in the brain tissue obviously decreased after medication in all the medicated groups in a dose-dependent manner, showing statistical difference (P < 0.05).

CONCLUSIONTPGs improved D-galactose induced aging rats' capability for learning and memory through regulating changes of TLR4 and IL-33 expressions.