Peptides in the brain.

More than 25 biologically active peptides have been identified in the CNS. They are involved in the regulation of complex cerebral functions such as sleep, ingestive and motor behavior, pain, cognition, emotions and mood. In view of the coexistence of peptides with classical transmitters in the same nerve endings of some central neurons the concept of cotransmission has been recently developed. The intervention of peptides in transmission and cotransmission processes opens very stimulating ways of research in the field of neurology and psychiatry.