Palisade endings in extraocular muscles of the monkey are immunoreactive for choline acetyltransferase and vesicular acetylcholine transporter.
OBJECTIVE
To analyze palisade endings in extraocular muscles (EOMs) of a primate species and to examine our previous findings in cat that palisade endings are putative effector organs.


METHODS
Eleven monkeys (Macaca fascicularis) of both sexes, between 4 and 6 years of age were analyzed. Whole EOM myotendons were immunostained with four combinations of triple-fluorescent labeling and examined by confocal laser scanning microscopy. Labeling included antibodies against choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), neurofilament, and synaptophysin. Muscle fibers were counterstained with phalloidin.


RESULTS
Palisade endings were observed in all monkey EOMs. Nerve fibers extended from the muscle into the tendon and looped back to divide into a terminal arborization (palisade ending) around a single muscle fiber tip. In approximately 30% of the cases, nerve fibers supplying palisade endings often established motor terminals outside the palisade complex. Nerve fibers forming palisade endings were ChAT-neurofilament positive. Axonal branches of palisade endings were ChAT-neurofilament positive as well. All palisade nerve terminals exhibited ChAT-synaptophysin immunoreactivity. Within the palisade complex, palisade nerve terminals exhibited VAChT immunoreactivity. All palisade nerve terminals were VAChT-synaptophysin immunoreactive.


CONCLUSIONS
The results confirm that in the monkey, palisade endings contain acetylcholine and are therefore most likely effector organs. Palisade endings are also present in human EOMs and because of their location at the myotendinous junction, these organs are of crucial interest for strabismus surgery.
Konakci
Kadriye Zeynep
KZ
Center of Anatomy and Cell Biology, Integrative Morphology Group, Medical University Vienna, Austria.
Streicher
Johannes
J
Hoetzenecker
Wolfram
W
Haberl
Ines
I
Blumer
Michael Josef Franz
MJ
Wieczorek
Grazyna
G
Meingassner
Josef Gottfried
JG
Paal
Szabolcs Levente
SL
Holzinger
Daniel
D
Lukas
Julius-Robert
JR
Blumer
Roland
R
D000818:Animals; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D008252:Macaca fascicularis; D008297:Male; D018613:Microscopy, Confocal; D009046:Motor Neurons / Q000378:metabolism; D009411:Nerve Endings / Q000378:metabolism*; D009412:Nerve Fibers / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D009475:Neurons, Afferent / Q000378:metabolism*; D009801:Oculomotor Muscles / Q000294:innervation*; D016708:Synaptophysin / Q000378:metabolism; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism*
D016900:Neurofilament Proteins; D016708:Synaptophysin; D050494:Vesicular Acetylcholine Transport Proteins; D002795:Choline O-Acetyltransferase