[Effects of botulinum toxin-A on facial motoneurons].
OBJECTIVE
To examine effects of botulinum toxin-A(BTX-A) intramuscular injection at rat whisker pad on facial motoneurons.


METHODS
A total of 54 male Sprague-Dawley rats were used in the present study. A single intramuscular injection of the BTX-A at rat whisker pad as model was employed, using retrograde labeling and immunohistochemical staining methods, to observe the effects of BTX-A on the facial motoneurons survival and the expression of choline acetyltransferase (ChAT) and vescular acetylcholine transporter (VAChT). Rats received intramuscular injection of 0.9% NaCl served as control.


RESULTS
The fluorescence labeled facial motoneurons were all in the lateral subnucleus of facial nucleus after BTX-A injection at rat whisker pad. There was no significant difference of labeled motoneuron number in BTX-A injection group vs control at observed time points (t = 0.022. P > 0.05). At 7 d after BTX-A injection, optical density of ChAT and VAChT immunostaining began to increase in facial motoneurons of the lateral subnucleus ipsilateral to the injection side. A maximal increase of this data was observed 14 d after injection; thereafter it declined gradually to normal level. The patterns of changes in optical density of ChAT and VAChT immunostaining in facial motoneurons of the lateral subnucleus contralateral to the injection side were similar to that of ipsilateral. There were significant difference of optical density of ChAT and VAChT immunostaining in facial motoneurons of the lateral subnucleus in BTX-A injection group vs control(t = 3.054, P < 0.05; t = 3.366, P < 0.05).


CONCLUSIONS
After BTX-A injection at rat one side whisker pad, the number of facial motoneurons innervating muscles of whisker pad in the lateral subnucleus has no change. However, the expression of ChAT and VAChT increase in the facial motoneurons of the lateral subnucleus. These data indicate that BTX-A intramuscular injection at facial nerve target organ doesn't induce the loss of facial motoneurons, and only results in the expression of protein related to acetylcholine changing.
Wang
Jinling
J
Department of Otorhinolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China. jinling-w@fmmu.edu.cn
Lu
Lianjun
L
Liu
Shunli
S
D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D002795:Choline O-Acetyltransferase / Q000096:biosynthesis*; D005154:Facial Nerve / Q000187:drug effects* / Q000378:metabolism; D007273:Injections, Intramuscular; D008297:Male; D026901:Membrane Transport Proteins; D009046:Motor Neurons / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins / Q000096:biosynthesis
D026901:Membrane Transport Proteins; C493461:Slc18a3 protein, rat; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D002795:Choline O-Acetyltransferase; D019274:Botulinum Toxins, Type A