Brain cell discovery may shed light on nervous system disorders
26 March 2008
The textbook view of neuroscience is that there are two main categories of cell in the brain and spinal cord: nerve cells, which carry information in the form of electrical signals called action potentials, and glial cells, which are ‘housekeeping’ cells that do not show electrical activity. But now, Professor David Attwell and colleagues from University College London and Dr Ragnhildur Káradóttir from the University of Cambridge have found a type of glial cell in rat brain that fires action potentials, just like nerve cells.
Glial cells coat nerve fibres in a fatty insulator called myelin, which allows electrical signals to pass through the nerve fibres quickly. The researchers looked at the precursor (stem) cells that generate these glial cells and found that, while the cells all looked the same, some - unexpectedly - were able to generate electrical signals.
By understanding more about how these two classes of glial cell are involved in the myelination of nerve fibres, researchers hope eventually to develop therapies that promote repair in situations where the myelin sheath is damaged, for example, in cerebral palsy, multiple sclerosis and spinal cord injury.
In the study, the researchers looked at how both classes of precursor cell responded to a brain chemical called glutamate, which is known to damage precursor cells in cerebral palsy (and possibly stroke and spinal cord injury). The cells that could produce electrical signals were preferentially damaged as they had more receptors for glutamate. This suggests that future therapeutic strategies should perhaps focus on this more ‘vulnerable’ class of cells.
The precursor cells examined in this research (oligodendrocyte precursor glia) make up 5 per cent of the cells in the adult brain. Because oligodendrocyte precursor glia can divide to produce new cells, transplants of the precursors could potentially have a role in repairing damaged myelin. Work is currently underway to identify which class of cell is involved in remyelination in disease states.
Image: Myelin wrapping axons entering the cerebellum; inset shows action potentials recorded from an oligodendrocyte precursor cell (R Káradóttir and D Attwell).
References
Káradóttir R et al. Spiking and nonspiking classes of oligodendrocyte precursor glia in CNS white matter. Nat Neurosci 2008; doi:10.1038/nn2060 [Epub ahead of print].