Effects of L-655,708 on expression changes of GABA, glutamate, and beta-endorphin induced by propofol anesthesia in rats

Abstract

Anesthetics are considered to be one of the important inducing factors of postoperative cognitive dysfunction (POCD). The hippocampal region of the rat is one of the action sites of general anesthesia drugs. L 655,708, a reverse agonist of gamma aminobutyric acid (GABA) receptor, can significantly improve short-term memory dysfunction in mice after anesthetized with isoflurane. So the purpose of this study is to investigate the effects of L-655,708 on expression of GABA, glutamate (GLU), and beta-endorphin (β-EP) in the dentate gyrus region of the hippocampus and cognition of rats anesthetized with propofol. In all, 30 male Sprague–Dawley (SD) rats were randomly allocated into the control group, sham group, and L-655,708 group, with 10 in each group. The cognitive function of rats was measured by Morris water maze before and 1 h after administration. Then the rats were sacrificed for brain tissues. Immunohistochemistry was used to study the expression of GABA, GLU, and β-EP in the hippocampus of anesthetized rats in each group. Compared with the control group, the latency of the sham group and L-655,708 group were significantly prolonged after administration ( P < 0.05). However, L-655,708 could shorten the prolonged latency ( P < 0.05). There was no significant difference in times of accessing original platform area between the three groups before and after medication ( P > 0.05). The expression level of GABA in the dentate gyrus region of hippocampus of rats in the sham group was significantly higher than that in the control group ( P < 0.05), while the expression level in the L-655,708 group was significantly lower than that in the sham group ( P < 0.05). No significant difference was found in the expression of GLU in the dentate gyrus region of hippocampus of rats in each group ( P > 0.05). Compared with the control group, the expression of β-EP was significantly lower in the dentate gyrus region of the hippocampus of sham group rats ( P < 0.05). However, the expression of β-EP in the L-655,708 group was significantly higher than that in the sham group ( P < 0.05). Cognitive dysfunction in rats anesthetized with propofol may be related to high expression of GABA and low expression of β-EP in the hippocampus. The mechanism of L-655,708 in reducing the cognitive impairment in propofol anesthetized rats may be bound up with down-regulating the expression of GABA and increasing the expression of β-EP in the hippocampus.