Descending dopaminergic fibres within the spinal cord originate in the A11. (A) Dopamine acts on all five dopamine receptors that are distributed non-uniformly through the dorsal and ventral horns of the spinal cord (Adapted with permission from Zhu et al., 2007). Descending noradrenergic fibres originating in the A5, A6 and A7 nuclei of the pons innervate the spinal cord. Schematic adapted with permission from Björklund and Dunnett (2007).  Dopamine: a parallel pathway for the modulation of spinal locomotor networks.  Whelan et al 2014.