Biology Reference
In-Depth Information
mechanism by which physical exercise might help peripheral nerve regen-
eration is by diminishing the amount of myelin-related inhibitors of axonal
growth (
Filbin, 2003; Gaudet, Popovich, & Ramer, 2011
). In mice, wheel
running decreased the levels of myelin-associated glycoprotein in the spinal
cord, while enhanced neurite outgrowth of cortical neurons growing on
myelin is collected from the running-trained animals (
Ghiani et al.,
2007
). The lowering action of running exercise on the levels of myelin-
associated glycoprotein in the spinal cord seems to be regulated by BDNF
and protein kinase A (
Ghiani et al., 2007
).
2.2.4 Enhanced nerve regeneration by conditioning exercise
Physical exercise seems to exert a conditioning effect over the nervous sys-
tem that potentiates its ability to respond to subsequent damage (
Bobinski
et al., 2011; Molteni et al., 2004
). Voluntary wheel running for a period
of just 3 and 7 days clearly enhanced the rate of neurite outgrowth in cul-
tured exercise-conditioned dorsal root ganglion neurons as well as increased
the number of sensory neurons regenerating following sciatic nerve injury
(
Molteni et al., 2004
). The conditioning effect of wheel running was
associated with higher BDNF and NT-3 expression in sensory ganglia of
sciatic-injured animals as well as with increased levels of synapsin I and
GAP-43. Such conditioning effect of treadmill exercise relied on neuro-
trophins signaling through tyrosine kinase receptors (
Molteni et al., 2004
).
Treadmill exercise conducted prior to sciatic nerve crush injury was also
reported to improve recovery of motor and sensitive function in mice, while
treadmill exercise performed both before and after the sciatic nerve injury
resulted in better morphology of the regenerated sciatic nerves, with
increased number of myelinated fibers and increased myelin thickness
(
Bobinski et al., 2011
). Together with the positive role on functional recov-
ery, conditioning treadmill exercise blunted the response of interleukin (IL)-
1
b
in both the regenerating sciatic nerve and the spinal cord, and of IL-6
receptor in the spinal cord, but not
in the sciatic nerve (
Bobinski
et al., 2011
).
2.3. Effect of passive physical exercise on nerve regeneration
and functional recovery
Passive exercise can be employed in the early stages of rehabilitation of PNS
injuries, commonly through manual limb mobilization. In an early study,
passive mobilization of the hindpaw, conducted before muscle rein-
nervation, was able to stimulate nerve sprouting, although it had no effect
