Behavioral assessment of depressive-like symptoms in a rodent model of spinal cord injury
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Spinal cord injury (SCI) currently affects over 250,000 people in the United States alone with approximately 11,000 new cases occurring each year. In addition to its debilitating physical consequences, spinal cord injury significantly impacts emotional and psychological well-being. This leads to an increased risk for depression in SCI patients. Previous studies have found the rate of major depressive disorder (MDD) among patients with SCI to be as high as 24%, compared with 8.95% in the general population. However, despite the prevalence of depression in human patients with SCI, there is no spinally injured animal model of depression. To address this issue, we used a battery of established behavioral tests (proposed to be indicative of depression-like behavior in rats) to assess depression following a moderate contusion injury. The proposed ethogram consisted of the sucrose preference test (SPT) and the forced swim test (FST), both common rodent paradigms for assessing depressive-like behavior. The battery also included open field activity, social exploration, and burrowing tasks. Subjects were acclimated on the tasks prior to injury and baseline scores were obtained on the two days immediately preceding injury. Testing was then conducted on days 1 and 2, 9 and 10, and 19-21. BBB scores of recovery of motor function, weight gain, and appetite were assessed for 21 days following injury. Results from a hierarchical cluster analysis indicated that the ethogram could be divided into four main behavioral categories: loss of interest/pleasure and motivation, psychomotor retardation, locomotor recovery, and general health. Depressed subjects displayed a greater loss of interest/pleasure and motivation in the sucrose preference test, social exploration test, and the forced swim test, when compared to non-depressed subjects. Depressed subjects also displayed greater psychomotor retardation in the burrowing task and open field test. Depression did not have an effect on recovery of locomotor function or weight gain. Future studies should examine other symptomatic behaviors including cognitive impairments and sleep disturbances. Future directions will be to examine the use of anti-depressants to reverse behaviors observed in depressed subjects. Additional studies should also consider the effects of anti-depressants on locomotor recovery and weight gain.
Luedtke, Kelsey 1988- (2011). Behavioral assessment of depressive-like symptoms in a rodent model of spinal cord injury. Honors and Undergraduate Research. Available electronically from