INVESTIGATING THE ROLE OF NEUROPEPTIDE Y IN THE VENTRAL HIPPOCAMPUS IN REGULATING RATS’ ELEVATED PLUS-MAZE AND SHOCK-PROBE BURYING BEHAVIOURS
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Neuropeptide Y (NPY) has recently gained interest as a potential regulator of anxiety-like behaviours. However, its anxiety-associated effects in the ventral hippocampus are not well known, even though this structure is also heavily implicated in anxiety regulation. The goal of this thesis was to investigate whether neuropeptide Y and its Y1 and Y2 receptors are associated with anxiety regulation in the ventral hippocampus. To determine whether NPY has a role in anxiety regulation in the ventral hippocampus, I infused rats with either NPY or vehicle control. Next, to determine whether the effects of NPY on anxiety-related behaviour are associated with the Y1 receptor, I infused rats with either the Y1 antagonist, BIBO 3304 or saline, followed by infusions of either NPY or saline just prior to testing (Experiment 2). In Experiment 3, I infused the Y2 antagonist, BIIE 0246 prior to infusions of either NPY or saline. In all experiments, the rats were tested in the elevated plus-maze (EPM) and the shock-probe burying test (SPBT). Infusions of NPY alone into the ventral hippocampus decreased rats’ shock-probe burying duration (p = .007), but did not affect rats’ open-arm exploration (Experiment 1). This pattern of findings was replicated in Experiment 2 and 3. The results demonstrate that infusions of NPY into the ventral hippocampus powerfully suppress defensive burying in rats, while not affecting their open-arm activity. This suppression of burying was attenuated by infusions of BIBO 3304 but not BIIE 0246, suggesting that this anxiolytic-like effect is associated with the Y1, but not Y2, receptor. Thus, NPY seems to have an anxiolytic-like effect in the ventral hippocampus, in a test-specific fashion, that is associated with the Y1 receptor.