After injury, spinal neurons establish specialized bridges to connect with other injured neurons, according to new findings from researchers at the University of Pennsylvania Medical Center. Interestingly, the injured cells reach out only to each other in this process, excluding healthy neighboring cells from the network. The bridges - called gap junctions - are commonly found among neurons during development but are rarely seen in the adult mammalian nervous system. A report on the study appears in the January 15 issue of the Journal of Neuroscience ( http://www.jneurosci.org/ ).

The results begin to suggest how connectivity between neurons in the spinal cord and between neurons and muscle might be re-established after peripheral nerve damage or spinal cord injury, areas for which current treatments are inadequate. The re-coupling of injured spinal neurons by gap junctions is similar to the coupling normally seen among neurons in developing animals. Finding ways to recapitulate this developmental phenomenon might therefore be an important part of future therapeutic efforts to rewire neurons and their targets after injury.

"Our study shows that neurons establish connection with other neurons after injury by creating bridges called gap junctions," says Rita J. Balice-Gordon, PhD, an assistant professor of neuroscience and senior author on the study. "The gap junctions are induced after nerve damage and may mediate electrical or biochemical communication between injured neurons."

"The presence of gap junctions could affect either neuronal activity or the exchange of second messengers and other small molecules," says Qiang Chang, BS, a graduate student in Balice-Gordon's laboratory and lead author on the study. "That, in turn, could encourage neuronal survival and promote rewiring after nerve injury."

The type of neurons investigated by the authors are the motor neurons in the spinal cord, the cells that control t
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Contact: Franklin Hoke
hokef@mail.med.upenn.edu
215-662-2560
University of Pennsylvania School of Medicine
12-Jan-2000