Affiliations: Research and Development Service, Hines VA Hospital,
Hines, IL 60141, USA | Department of Cell Biology Neurobiology and Anatomy,
Loyola University Chicago, Maywood, IL 60153, USA
Abstract: Purpose: Testosterone (T) treatment accelerates recovery from facial
paralysis after facial nerve crush in hamsters. In this study, we extended
those studies to another injury model and asked the following question: Will T
treatment accelerate recovery from lower limb paralysis following sciatic
nerve crush in the rat? Methods: Castrated adult male rats received a right
side sciatic nerve crush at the level of the sciatic notch, with the left side
serving as control. Half the animals received a subcutaneous implant of a
propionated form of T (TP), the others were sham-implanted. Weekly testing
using the Sciatic Functional Index (SFI), a quantitative measure of locomotion,
was done for 7 weeks postoperative (wpo). Results: Between 3 and 5 weeks
post-op, the average SFI score of the TP-treated group was higher than
controls. This difference was significant at 4 wpo, indicating an accelerated
degree of functional recovery. At these timepoints, the differences were
attributable to the footprint or paw length and associated with calf muscle
reinnervation rather than the toespreading component associated with intrinsic
foot muscle rein-nervation. Beyond 5 wpo, there were no differences in the SFI
scores. Conclusion: The results indicate that, as with facial nerve
regeneration in the hamster, testosterone accelerates functional recovery from
hind limb paralysis following sciatic nerve injury in the rat. While the
responses of spinal motoneurons to injury can differ from those of cranial
motoneurons, in this case it appears that they share a similar response to the
trophic actions of androgen. This is important in the context of designing
therapeutic strategies for dealing with direct trauma to motoneurons resulting
from both peripheral and central nervous system trauma, such as spinal cord
injury.
