Distribution of non-opioid peptides in the mammalian CNS: relationship to monoamine neurotransmitter systems.

The distribution of many peptides throughout the mammalian CNS has been described. This report will review immunocytochemically-defined non-opioid peptide systems in relation to the more established monoamine systems. Immunocytochemical localization, especially when combined with intraneuronal tracing techniques, provides information about possible interactions among neuronal systems including terminations associated with the cell bodies of other systems, common terminal fields, or co-localization within the same neurons. For example, many peptide and monoamine systems send parallel descending projections to the spinal cord. The origins of many of these spinal cord projections within specific brainstem nuclei are known and will be described. The elucidation of chemically defined anatomical connections within the central nervous system (CNS) is an immense but necessary undertaking in the understanding of CNS involvement in normal and abnormal physiological and behavioral processes.