Neuropharmacology. 2011 Jan 17.

The role of propriospinal interneurons in recovery from spinal cord injury.

Flynn JR, Graham BA, Galea MP, Callister RJ.

School of Biomedical Sciences and Pharmacy, Faculty of Health and Hunter Medical Research Institute, The University of Newcastle, Callaghan, NSW 2308, Australia.

Over one hundred years ago, Sir Charles Sherrington described a population of spinal cord interneurons (INs) that connect multiple spinal cord segments and participate in complex or 'long' motor reflexes. These neurons were subsequently termed propriospinal neurons (PNs) and are known to play a crucial role in motor control and sensory processing. Recent work has shown that PNs may also be an important substrate for recovery from spinal cord injury (SCI) as they contribute to plastic reorganisation of spinal circuits.Here we summarise the anatomy, organisation and function of PNs in the uninjured spinal cord, briefly outline the pathophysiology of SCI, describe how PNs contribute to recovery of motor function, and finally, we discuss the mechanisms that underlie PN plasticity.The location, intersegmental projection pattern and sheer number of PNs mean that after SCI, a significant number of them are capable of 'bridging' an incomplete spinal cord lesion. When these properties are combined with the capacity of PNs to activate and coordinate locomotor central pattern generators (CPGs), it is clear they are ideally placed to assist locomotor recovery. We propose there are two major challenges for PN research. The first is to learn more about ways we can promote PN plasticity and manipulate the 'hostile' micro-environment that limits regeneration in the damaged spinal cord.The second is to study the cellular/intrinsic properties of PNs to better understand their function in both the normal and injured spinal cord.