title: Molecular characteristics suggest an effector function of palisade endings in extraocular muscles.
abstract: OBJECTIVE
  To analyze palisade endings in cat extraocular muscles (EOMs) and to clarify whether these EOM-specific organs are sensory or motor.
  
  
  METHODS
  Twelve cats aged between 1 and 16 years were analyzed. Whole EOM tendons were immunostained using four different combinations of triple fluorescence labeling. Triple labeling included antibodies against choline acetyltransferase (ChAT), neurofilament, synaptophysin, and alpha-bungarotoxin. Preparations were examined by confocal laser scanning microscopy. ChAT-labeled EOMs were also analyzed by immunoelectron microscopy. Three-dimensional reconstructions were made of palisade endings.
  
  
  RESULTS
  Palisade endings were found in the distal and proximal myotendinous regions of cat EOMs. These endings arose from thin nerve fibers coming from the muscle and extending into the tendon. There, the nerve fibers turned back 180 degrees to divide into terminal branches around the muscle fiber tips. Terminal branches established numerous contacts with the tendon attached to the muscle fiber tip and only a few contacts with the muscle fiber. Often, nerve fibers forming palisade endings on muscle fiber tips were observed to establish multiple motor contacts on muscle fibers outside palisade endings. Three-dimensional reconstructions depicted the complex morphology of the palisade endings. All nerve fibers supplying palisade endings stained positively for ChAT and neurofilament. All nerve terminals in palisade endings were ChAT and synaptophysin positive. Only neuromuscular contacts in palisade endings were positive for alpha-bungarotoxin, as well.
  
  
  CONCLUSIONS
  This study provides evidence that palisade endings in cat EOMs have effector function. The findings may be of significance for strabismus surgery because palisade endings are also found in human EOMs.
authors.affiliation: Center of Anatomy and Cell Biology, Integrative Morphology Group, Vienna, Austria.
authors.forename: Kadriye Zeynep
authors.initials: KZ
authors.lastname: Konakci
authors.forename: Johannes
authors.initials: J
authors.lastname: Streicher
authors.forename: Wolfram
authors.initials: W
authors.lastname: Hoetzenecker
authors.forename: Michael Josef Franz
authors.initials: MJ
authors.lastname: Blumer
authors.forename: Julius-Robert
authors.initials: JR
authors.lastname: Lukas
authors.forename: Roland
authors.initials: R
authors.lastname: Blumer
mesh_terms: D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism; D002415:Cats; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D005260:Female; D021621:Imaging, Three-Dimensional; D008297:Male; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism; D009411:Nerve Endings / Q000166:cytology* / Q000378:metabolism; D009412:Nerve Fibers; D016900:Neurofilament Proteins / Q000378:metabolism; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism; D009801:Oculomotor Muscles / Q000294:innervation*; D010590:Phalloidine / Q000378:metabolism; D016708:Synaptophysin / Q000378:metabolism
chemical_list: D002038:Bungarotoxins; D016900:Neurofilament Proteins; D016708:Synaptophysin; D010590:Phalloidine; D002795:Choline O-Acetyltransferase