Effect Of Mental Stress On Hippocampal Volume And Metabolin Level In Rats In Vivo: A Study Of Magnetic Resonance Imaging And Spectroscopy

Introduction and Objective: The reliable evaluation of mental injury has been a difficult problem in forensic psychiatry, because of subjective, unstable and equivocal results. This study explore the neurochemistry mechanism of hippocampal damage induced by psychological stress, and the relationship between hippocampal volume,NAA level and stress responses by Magnetic resonance imaging (MRI) and spectroscopy (MRS) in oder to provide experimental basis for the evaluation of mental injury in human.Materials and Methods: 36 adult male Sprague-Dawley rats were randomly divided into 6 groups (n=6 each group): control group, single stress group, 2-week stress group, 4-week stress group, tianeptine group with 4-week stress, and saline group with 4-week stress. Forced swimming test was used as stressor. Behaviors were tested with the open-field test and rats' bodyweight were measured at the beginning and end of stress. Corticosterone level was measured by enzyme linked immunosorbent assay (ELISA). MRI and MRS were used to detect the volume of hippocampal and NAA concentration in vivo. NAA level in hippocampus were measured by high performance liquid chromatography (HPLC) coupled with ultraviolet detection. The data were analyzed by one-way analysis of variance (ANOVA), t test with SPSS11.0 for Windows.Results: (1) Behavior and corticosterone changes: Compared with the number of crossing of 2-week stress group and 4-week stress group, control group is significant different from that of other groups; Compared to control group,2-week stress group and 4-week stress group, single stress group has much more number of decorating and rearing (p<0.05, p<0.01 respectively) . Serum corticostrone of control group is significant different to other groups.The stress intensity has negative relation to crossing, rearing, decorating, locomotive amount and time (p<0.05), while positive relation to rest time (p<0.01). Serum corticosterone concentration is relate negativly to locomotive amount and time (p<0.05), while relate positivly to rest time (p<0.01).(2) Impact of stress on volume and NAA concentration of rats' hippocampus: Via observation in vivo, 4-week stress group rats have much smaller hippocampus and lower NAA concentration than the control group, single stress group and 2-week stress group; the volume and NAA level of rats' hippocampus are negatively correlated to the stress intensity in vivo as well as in vitro, but the adminitration of tianeptine may turn over this trend.(3) Impact of stress on Choline (Cho) levels of rats' hippocampus: There is no difference...