"Preface Over the past four decades, the number of peptides identified as neurotransmitters or neuromodulators in the central and peripheral nervous systems has significantly increased. These compounds, known as neuropeptides, have been recognized for playing an important role in the communication between cells in a variety of neuronal networks. Although, a considerable number of neuropeptides have been characterized so far, their quantity is limited compared to the number of precursor proteins that are actually found to be expressed in cells of the nervous system. Numerous studies have confirmed that neuropeptides are involved in a number of biological activities. These include modulation of brain reward, pain processing, and immune response, as well as neuroendocrine regulations, control of neurovegetative functions, and trophic effects. In recent years, it has become evident that the role of neuropeptides as fast-acting neurotransmitters is challenged by the observation that many of them may act as growth factors by stimulating cell proliferation and slow-acting mitogenesis. It has thus been demonstrated that a number of neuroactive peptides, such as pituitary adenylate cyclase-activating polypeptide (PACAP), adrenocorticotrophin (ACTH), opioid peptides, somatostatin, and substance P, may modulate proliferation and cell viability. Some peptides act as stimulatory factors on brain circuits involved in cognition, whereas others may act as inhibitory factors. Accordingly, many neuropeptide systems appear as important targets for neuroprotective drugs and drugs that promote neuroregeneration"--Provided by publisher.