Making the right connections

Release date: 12-Dec-2009

Organisation: Center for Neural Repair, University of California

A new study led by Professor Mark Tuszynski at the University of California shows regenerating nerve fibres can be directed to appropriate cells amongst millions of possible targets after spinal cord injury.

Researchers examined the effect of a growth factor called neurotrophin-3 (NT-3) on directing growth of nerve fibres in rats with spinal cord injury.

NT-3 released by the correct target cell as a cue for guiding nerve fibres, known as axons, allowed formation of new junctions between nerve cells known as synapses.

When NT-3 was produced in the wrong target cell, axons also followed the growth factor and grew into the wrong region.

Regeneration required two other treatments at the same time. A cell bridge in the spinal cord injury site was needed to support axon growth. Also, a specific stimulus to the injured nerve cell was required to turn on growth genes.

Using high-resolution imaging, the researchers showed that regenerating axons directed to the correct cell formed synapses exactly on target. These axons contained tiny sacs full of the chemical messengers needed to support electrical activity between the new nerve connections.

However, the team found these connections were not active. Further work revealed it was likely due to lack of myelin covering the regenerating axons. Myelin is an insulating sheath which helps electrical impulses travel efficiently to the brain.

Source: Taylor, et al. (2009) Chemotropic guidance facilitates axonal regeneration and synapse formation after spinal cord injury. Nature Neuroscience, 12(9); 1106 - 1113.



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