The role of serotonin in reflex modulation and locomotor rhythm productionin the mammalian spinal cord

Over the past 40 years, much has been learned about the role of serotonin i n spinal cord reflex modulation and locomotor pattern generation. This revi ew presents an historical overview and current perspective of this literatu re. The primary focus is on the mammalian nervous system. However, where re levant, major insights provided by lower vertebrate models are presented. R ecent studies suggest that serotonin-sensitive locomotor network components are distributed throughout the spinal cord and the supralumbar regions are of particular importance. In addition, different serotonin receptor subtyp es appear to have different rostrocaudal distributions within the locomotor network. It is speculated that serotonin may influence pattern generation at the cellular level through modulation of plateau properties, an interpla y with N-methyl-D-aspartate receptor actions, and afterhyperpolarization re gulation. This review also summarizes the origin and maturation of bulbospi nal serotonergic projections, serotonin receptor distribution in the spinal cord, the complex actions of serotonin on segmental neurons and reflex pat hways, the potential role of serotonergic systems in promoting spinal cord maturation, and evidence suggesting serotonin may influence functional reco very after spinal cord injury. (C) 2001 Elsevier Science Inc.