Neuropeptide Y ( NPY) is the most abundant active peptide in the body. Outside the brain NPY is a co-transmittor with noradrenaline ( NA) in sympathetic nerve endings. High release of NPY occurs when peripheral sympathetic nerves discharges at high frequencies , e.g stress situations eliciting sudden cardiac death or aggravation of heart failure. Peripheral NPY has a multitude of effects. The schematic figure above shows two important effects: 1) peripheral vasoconstriction, mediated by Y1 receptors and 2) inhibition of acetylcholine release from e.g vagal nerve endings in the heart mediated by Y2 receptors. Effects mediated by NPY are much more longlasting than those mediated by NA.
To be contiued!