Neuropeptide Y (NPY) is a 36 amino acid peptide neurotransmitter, which is widely expressed in the central and peripheral nervous systems of mammals. Neuropeptide Y has an important role in the stimulation of the appetite and is relevant to the pathophysiology of anxiety and depressionNeuropeptide Y is one of the most potent stimulators of feeding. At least five distinct G-protein coupled receptors (Y1, Y2, Y4, Y5, and Y6) mediate the actions of NPY. In rodents, repeated administration of Neuropeptide Y leads to hyperphagia and obesity associated with decreased thermogenesis in brown adipose tissue, hyperinsulinemia, hypercorticosteronaemia, reduced plasma testosterone concentrations, and insulin resistance in skeletal muscle. In the cardiovascular system Neuropeptide Y is found in neurons supplying the vasculature, cardiomyocytes, and endocardium, and is involved in physiological processes including vasoconstriction, cardiac remodeling, and angiogenesis. It is increasingly also implicated in cardiovascular disease pathogenesis, including hypertension, atherosclerosis, ischemia/infarction, arrhythmia, and heart failure. Neuropeptide Y is considered to be an anxiolytic endogenous peptide and its levels can be modulated by stress and it may also play a role in the etiology and pathophysiology of posttraumatic stress disorder.