Effects of hyperbaric oxygen treatment on glucocorticoid receptor expression in the hipopocampus and on the behavior of rats under chronic restraint stress

Abstract

Objective To explore the effects of hyperbaric oxygen treatment on chronic stress and glucocorticoid receptor (GR) expression in the hippocampus. Methods A total of 60 male Wistar rats were randomly divided into a restraint group, an HBO (hyperbaric oxygen) group, an HBO-restraint group and a control group using a random number table, each group with 15 animals. All the rats in the restraint and HBO groups were constrained by immobilizing their fore- and hind-limbs on a self-made frame for 3h daily for 21 days, and those in the HBO group received HBO treatment once daily for the same 21 days. The HBO-restraint group was immobilized in the morning and treated with HBO in the afternoon. The control group was reared without any special intervention. On the 1st, 11th and 21st day of treatment, rats from the different groups were assessed using the open field test. On the 21st day, all the animals were sacrificed and their brains were harvested to detect GR expression. Results In the open field test on the 11th day, the restraint group scored (131.0±20.6) in terms of motor level and (26.5±4.6) for exploratory behavior, both significantly higher than before restraint and significantly higher than those in the HBO-restraint group at the same time point. Immunofluorescence assay showed that GR expression in the hippocampus of the restraint group was significantly decreased compared with the control group. There was no significant difference, however, between the HBO-restraint group and the control group. Conclusion Chronic restraint stress induces changes in behavior and GR expression in rats which can be alleviated by hypbaric oxygen treatment. Key words: Chronic stress; Hyperbaric oxygenation; Chronic restraint; Open-field test; Receptors, glucocorticoid