Unilateral Lesions of the Hippocampus Result in Circling Behavior: Effects on the Dopamine System

Abstract

Rotational behavior, induced by unilateral lesions of a number of brain regions has long been studied as a model of various dopamine- (DA) related diseases. The hippocampal formation is interconnected with many of the brain's DA systems and is therefore potentially involved in modulation of DA-related diseases. The present study investigates unilateral hippocampal lesions, generated with either kainic acid (KA) and ibotenic acid (IBO), and subsequent rotational behavior. The results demonstrate that animals with unilateral KA hippocampal lesions exhibit significantly more rotation towards the side of the lesion immediately following surgery than either IBO lesioned animals or controls. Challenges with DA agonists at least 2 weeks postsurgery did not induce significant differences in rotational behavior. It appears that the former finding is a viable phenomenon which deserves further study.