Changes in the expression of actin and actin-binding protein in the brain of morphine dependent rats

Aim To investigate the expression of actin and actin-binding protein p-cofilin in several brain regions of morphine dependent rats.Methods Fourty-two male SD rats were randomly divided into morphine dependent 1 week group(group M1),morphine dependent 2 weeks group(group M2) and morphine dependent 4 weeks group(group M4) with 7 animals in each group.Every morphine dependent group had corresponding control group.In morphine dependent group the animals were given intraperitoneally increasing doses of morphine starting from 5,10,15,20,30,40,50 mg·kg-1 three times a day for 7 days.Rats in control group received the equal volume of saline.In group M2 and group M4 the animals received continuously 50 mg·kg-1 morphine injection once a day for 1 or 3 weeks respectively.Rats were sacrificed by decapitation 5 hours after the last injection.The brain regions including prefrontal cortex,hippocampus,striatum and thalamus were separated and frozen until assay.The expression of actin and actin-binding protein p-cofilin in several brain regions of rats were determined by Western blot.Results Compared with the control group,the ratio of F-actin to G-actin in prefrontal cortex of group M2 and group M4 was up-regulated by 53%(P0.05) and 102%(P0.01) respectively.The expression of p-cofilin in prefrontal cortex of group M2 and group M4 was up-regulated by 93%(P0.01) and 88%(P0.01) respectively.The ratio of F-actin to G-actin in hippocampus of group M4 was up-regulated by 94%(P0.01).The expression of p-cofilin in hippocampus of group M2 and group M4 was up-regulated by 45%(P0.05)and 30%(P0.05)respectively.The expression of p-cofilin in striatum of group M2 and group M4 was down-regulated by 25%(P0.05)and 30%(P0.05)respectively.Conclusion Chronic morphine treatment can induce the development of morphine dependence,which accompanies with actin rearrangments in the brain of rats in time-dependent and brain region-dependent way.