Cell death of spinal interneurones

The occurrence of neuronal death during development is well documented for some neuronal populations, such as motoneurones and dorsal root ganglion ce lls, whose connecting pathways are clearly defined. Cell survival is though t to be regulated largely by target and input connections, a process that s erves to match the size of synaptically linked neuronal populations. Far le ss is known about interneurones. It is assumed that most interneurone popul ations are excluded from this process because their connections are more di ffuse. Recent studies on the rat spinal cord have indicated that interneuro ne death does occur. both naturally during development and induced followin g peripheral nerve injury. Here the evidence for spinal interneurone death is reviewed and the factors influencing it are discussed. There are many fu nctional types of interneurones in the spinal cord that may differ in vulne rability to cell death, but it is concluded that for most spinal interneuro nes the traditional view of target regulation is unlikely. Instead it is pr oposed that developmental interneurone death in the spinal cord forms part of a plastic response to altered sensory activation rather than a size-matc hing exercise. There is also emerging evidence that interneurone death may play a more direct role in some neurodegenerative diseases than hitherto co nsidered. (C) 2000 Elsevier Science Ltd. All rights reserved.