The Effects of Intra-Cerebral Neuropeptide Y Infusion into the Ventral Hippocampus on Anxiety-Like Behaviour in the Elevated Plus-Maze

Neuropeptide Y (NPY) is one of the most prominent and evolutionarily conserved peptides in the mammalian nervous system. The hippocampus, which contains high densities of NPY producing cells and receptors, is considered a primary structure in the neuroanatomical circuitry of anxiety. Although once considered a homogenous structure, the ventral aspect of the hippocampus is now considered to play a more explicit role in anxiety regulation. To date there is no direct evidence implicating ventral hippocampal NPY in anxiety modulation. By contrasting the defensive behaviours of rats (N=24) in the elevated plus-maze (EPM) model of animal anxiety following intra-cerebral infusions of either experimental NPY (n=12), or saline (n=12), I expect that NPY infusions into the ventral hippocampus will cause marked reductions in anxiety-like behaviour. Specifically, NPY infusions at that site will increase the proportion of entries into, and time spent in, the open arm sections of the EPM, as well as decrease secondary defensive behaviours such as stretch-attend and flatback postures, head-dipping, and sniffing, while in protected portions (walled arms) of the EPM.