Dynamic changes of hippocampai volumes by MRI in rat depression models and their behavior changes before and after antidepressant treatment

Abstract

Objective To explore the dynamic changes of hippocarnpal volumes by MRI and their behavioral changes in rat depression models before and after antidepressant treatment, and their significance. Methods Based on the evaluation of ethology, 80 SD rats were randomly divided into 3groups: control group (n=10), depression group (n=10), and treatment group (n=60) which was equally divided into 3 subgroups (group A, B and C), given 2 different treatments as self-recovery or Fluoxetine intraperitoneal injection in the 4th, 6th and 8th week. The depression models were established by chronic unpredictable mild stress or isolated feeding for 8 weeks. The body weight and fluid consumption were measured before the antidepressant treatment and every 2 weeks of the treatment, and Morris water maze test was performed and the bilateral hippocampal volumes by high field MRI were measured before and after the antidepressant treatment and every 2 weeks of the treatment. Results The behavioral data indicated that the rat depression models were established successfully and these indexes were changed dynamically. In the 4th week, as compared with those of the control rats, the left hippocampal volumes of depression rats were significantly decreased (P＜0.05), while the right ones were not significantly different. In the 6th week, as compared with those of the control rats, the right ones began to significantly decrease the volume (P＜0.05), and the left ones kept decreasing. By self-recovery, the ethology changed better in the prophase but worsened in the mid-late phase, and the hippocampal volumes had no significant change. By Fluoxetine treatment, the ethology changed better, and the left hippocampal volumes had significant changes only in the prophase. Conclusion The behavior and hippocampal volumes in rat depression models change dynamically, and after treatment, the ethology and hippocampal volumes change differentially. Key words: Depression; Behavior; Hippocampus; MRI