Neuropeptide Y neurotransmitter molecule. Molecular model showing the structure of the neurotransmitter neuropeptide Y (NPY). NPY is found in the brain and autonomic nervous system. It is secreted by the hypothalamus and its main effect is to increase food intake and decrease physical activity. It has also been associated with a number of physiologic processes in the brain, including the regulation of energy balance, memory and learning, and epilepsy.