Lesions of supramammillary nucleus decreae self-grooming behavior of rats placed in an open field

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Aim : Although subcortical regions send numerous efferent fibers to the hippocampus, their involvementin hippocampal functions has not been fu11y elucidated. The aim of this study was to determine theefTect of the supram ammillary nucleus (SuM) on the hippocampus. Methods : Neurons within the SuMof rats were destroyed by local injections of an excitotoxin, ibotenic acid, and the efTects of theSuM-lesion on behaviors in an open field were investigated. Results: SuM lesions increased distancetraveled, movement time and latency to start grooming, while they decreased time spent grooming. SuMlesions had no efTect on rearing frequency or immobility time. Conclusion : Prolonged exploration anddecrease in the total time spent grooming observed in the SuM-lesioned rats were consistent with thebeh avi oral characteri stics of hippocamp al -lesioned rats of the previ ous report s, suggesting that the SuMis involved in the establishment of spatial memory by hippocampus during the initial exploration of anovel environment. In addition, the reduction of grooming in the SuM-lesioned animal suggests thatSuM may be involved in emotion, such as anxiety. The results ofthis study show the involvement oftheSuM in hippocampal function and in anxiety perceived in anovel environment.
2011-08-01