23 Neuropeptide Y in Brain Function

Neuropeptide Y (NPY), a 36‐amino‐acid peptide is abundantly expressed throughout the mammalian nervous system including: neocortex, hippocampus, striatum, amygdala, hypothalamus, thalamus, and brain stem. NPY has been implicated in the regulation of a number of different behaviors and neurophysiological functions, many of them part of the complex system(s) involved in maintaining and regulating homeostasis. These include, among others, anxiety and stress related responses, feeding, learning and memory, endocrine function, and circadian rhythms. The functions are mediated via different receptor subtype populations (Y1–y6), all belonging to the G‐protein‐coupled receptor super‐family. The Y1 subtype has been shown to mediate the anxiolytic effects of NPY, while the Y2 subtype is involved in regulation of circadian rhythms and neuronal excitability in the hippocampus, and may thus be the receptor subtype involved in the peptide’s effects on memory function. Stimulation of food intake by NPY has been proposed to be mediated by Y5 and/or Y1 receptors within the hypothalamus. Here, we present a summary of current findings concerning the central nervous system (CNS) functions of NPY in the context of homeostasis and reaction to the environment. List of Abbreviations: AA, amino acids; bp, base pair; CNS, central nervous system; CPON, C‐flanking peptide of NPY; CRF, corticotropin‐releasing factor; CSF, cerebrospinal fluid; GABA, gamma‐aminobutyric acid; HPA, hypothalamic–pituitary–adrenal (axis); ICV, intracerebroventricular; IV, intravenously; NPY, neuropeptide Y; NPY‐LI, NPY‐like immunoreactivity; PCR, polymerase chain reaction; PP, pancreatic polypeptide; PVN, paraventricular nucleus; PYY, peptide YY; SCN, suprachiasmatic nucleus; SNP, single nucleotide polymorphism