Abstract SNACC-35

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Long-term pattern of depression after traumatic brain injury using a sucrose preference test in rats

1Gruenbaum B, 2Boyko M, 2Zvenigorodsky V, 2Brotfain E, 2Zlotnik A
1Yale University School of Medicine, New Haven, CT, USA; 2Soroka Medical Center, Ben-Gurion University of the Negev, Beer Sheva, , Israel

Introduction: Depression is common after traumatic brain injury (TBI), and is a great source of disability. The incidence of depression after TBI ranges from 14% to 42% within the first year and from 11% to 61% at various time points up to 50 years after the injury. Depression is often correlated with an increased risk of suicide of harming others, as well as occupational and social dysfunction. Animal models and preclinical tests have been vital for the development of antidepressant therapies. Most studies examined depression at one single time point after injury, and did not evaluate long-term changes. The goal of this study was to examine the development of post-TBI depression in rats using a sucrose preference test, and to monitor changes in depression over time.
Materials and methods: 30 Wistar rats were randomly assigned to one of 2 groups. The first group was subjected to TBI, and the second group was a control (sham) group. TBI was induced with a weight drop model that is known to cause diffuse brain injury. 1h after injury, the TBI group underwent neurological assessment using neurological severity score (NSS) and only rats with a NSS > 7 were included in the experiment. After an acclimatization period, all rats subjected to a sucrose preference test at 1, 2, 4, and 6 month after brain injury. The test was conducted in following order: rats were housed in individual cages and given free access to the two bottles containing 100 ml of sucrose solution (1 %, w/v) and 100 ml of water, respectively. After 4 h, the volume (in milliliters) of both the consumed sucrose solution and water were recorded, and sucrose preference was calculated as sucrose preference (%) = sucrose consumption (ml) / (sucrose consumption [ml] + water consumption [ml]) × 100 %.
Results: Rats in the TBI group (n=10) demonstrated a significantly lower sucrose preference at 1, 2, and 4 month after brain injury comparing to the control group (n=10) (P<0.01). 6 month after injury, the rats demonstrated improvement in sucrose preference that was similar to the control group. Rats in the control group did not exhibit any changes in sucrose preference during the 6 months of the study.
Conclusion: In this study we demonstrated for the first time the long-term patterns of post-TBI depression using a sucrose preference test. The sucrose preference test is a reliable, simple, and highly sensitive model to study depression. Our findings reveal novel insights into the natural course of post-TBI depression, and can be useful for both for the study of mechanisms of depression and for the development of new antidepressant drugs. A reliable animal model of post-TBI depression allows for further investigations of the pathophysiology and treatment of this disorder.

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