Role of descending aminergic pathways in the development of locomotion.

The development of locomotor function in terrestrial higher vertebrates takes place during both the embryonic period and the first days (or weeks, depending on the species) of postnatal life. It relies on the maturation of different elements such as musculoskeletal system, sensory systems, network connectivity, and neuronal intrinsic properties. This maturation results from the interplay between genetic determinants and activity dependent processes. Numerous studies have shown that aminergic (serotonin, noradrenaline, dopamine) projections to the spinal cord could contribute to the maturation of locomotor networks. In this review we will describe the development of aminergic projections in the spinal cord of higher terrestrial vertebrates, and we will review literature describing the trophic role played by these pathways on different parameters of locomotor function.