Manual stimulation of the suprahyoid-sublingual region diminishes polynnervation of the motor endplates and improves recovery of function after hypoglossal nerve injury in rats.
BACKGROUND
Using the rat facial nerve axotomy model, the authors recently showed that manual stimulation of denervated whiskerpad muscles reduced the posttransectional polyinnervation at the neuromuscular junctions and promoted full recovery of vibrissal whisking.


OBJECTIVE
Prompted by implications for rehabilitation therapy, the authors examined whether manual stimulation of denervated supra- and infrahyoid muscles would also improve recovery after unilateral lesion on the hypoglossal nerve.


METHODS
Adult rats underwent transection of the right hypoglossal nerve. Half of the animals received no postoperative treatment, and the other half were subjected to daily manual stimulation of the suprahyoid/sublingual region for 2 months. Recovery was assessed by measuring the angle of tongue-tip deviation from the midline, degree of collateral axonal branching at the lesion site (counts after retrograde labeling with 2 fluorescent dyes), synaptic input to the hypoglossal motoneurons using synaptophysin immunocytochemistry, tongue-muscles motor representation in the cerebral cortex after c-Fos immunocytochemistry, and portion of polyinnervated neuromuscular junctions.


RESULTS
In animals receiving manual stimulation, the tongue-tip deviation was 37.0 +/- 49.37 degrees , whereas values in control nonstimulated rats were significantly higher (50.1 +/- 9.01 degrees ; P < .05; mean +/- SD). Improved recovery was not associated with reduced collateral axonal branching; there were also no differences in tongue-muscles representation in the motor cortex. However, manual stimulation restored the total synaptic input to levels in intact animals and reduced the proportion of polyinnervated neuromuscular junctions compared with nonstimulated animals.


CONCLUSIONS
The data show that manual stimulation of denervated muscles improves functional outcome following peripheral nerve injury. This suggests immediate potential for enhancing clinical rehabilitation strategies.
Evgenieva
Emilia
E
Faculty of Pre-School and Primary School Education, Sofia University, Bulgaria.
Schweigert
Patrick
P
Guntinas-Lichius
Orlando
O
Pavlov
Stoyan
S
Grosheva
Maria
M
Angelova
Srebrina
S
Streppel
Michael
M
Irintchev
Andrey
A
Skouras
Emmanouil
E
Kuerten
Stefanie
S
Sinis
Nektarios
N
Dunlop
Sarah
S
Radeva
Victoria
V
Angelov
Doychin N
DN
D000578:Amidines; D000704:Analysis of Variance; D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D020437:Hypoglossal Nerve Diseases / Q000473:pathology / Q000503:physiopathology* / Q000534:rehabilitation*; D009045:Motor Endplate / Q000503:physiopathology / Q000601:surgery*; D009046:Motor Neurons / Q000473:pathology; D009048:Motor Skills / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000502:physiology*; D013266:Stilbamidines; D014059:Tongue / Q000473:pathology; D014404:Tubulin / Q000378:metabolism
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D000578:Amidines; D002038:Bungarotoxins; D013266:Stilbamidines; D014404:Tubulin; C031455:diamidino compound 253-50