Neuropeptide Y (NPY)

Neuropeptide Y (NPY) is a 36-amino acid neuropeptide that acts as a neurotransmitter and neuromodulator in both the central and peripheral nervous systems. It is one of the most abundant peptides in the mammalian brain, with high concentrations found particularly in the hypothalamus and hippocampus. NPY plays critical roles in regulating physiological processes such as food intake, energy metabolism, stress response, blood pressure regulation, circadian rhythms, immune modulation, and neuroendocrine secretion. NPY exerts its effects through interaction with G protein-coupled receptors (GPCRs), specifically known as NPY receptors (Y1, Y2, Y4, Y5).

NPY exerts its effects through interaction with G protein-coupled receptors (GPCRs) primarily coupled to Gi/o proteins. Upon activation, they inhibit adenylate cyclase activity leading to decreased cAMP levels. They also modulate intracellular calcium levels via phospholipase C activation (notably through the Y1 receptor). Some subtypes can also couple to Gq proteins to increase IP3 production via PLCβ activation.