Ascending pathways that mediate cholinergic modulation of lumbar motor activity

Deciphering neuronal pathways that reactivate spinal central pattern generators ( CPG s) and modulate the activity of spinal motoneurons in mammals in the absence of supraspinal control is important for understanding of neural control of movement and for developing novel therapeutic approaches to improve the mobility of spinal cord injury patients. Previously, we showed that the sacral and lumbar cholinergic system could potently modulate the locomotor CPG s in newborn rodents. Here, we review these and our more recent studies of sacral relay neurons with lumbar projections to the locomotor CPG s and to lumbar motoneurons and demonstrate that sacral and lumbar cholinergic components have the capacity to control the frequency of the locomotor CPG s and at the same time the motor output of the activated lumbar motoneurons during motor behavior. A model describing the suggested ascending sacro‐lumbar connectivity involved in modulation of the locomotor rhythm by sacral cholinergic components is proposed and discussed. This is an article for the   special issue XVth International Symposium on Cholinergic Mechanisms .