TY - JOUR
T1 - Axons giving rise to the palisade endings of feline extraocular muscles display motor features
AU - Zimmermann, Lars
AU - Morado-Díaz, Camilo J
AU - Davis-López de Carrizosa, María A
AU - de la Cruz, Rosa R
AU - May, Paul J
AU - Streicher, Johannes
AU - Pastor, Ángel M
AU - Blumer, Roland
PY - 2013/2/13
Y1 - 2013/2/13
N2 - Palisade endings are nerve specializations found in the extraocular muscles (EOMs) of mammals, including primates. They have long been postulated to be proprioceptors. It was recently demonstrated that palisade endings are cholinergic and that in monkeys they originate from the EOM motor nuclei. Nevertheless, there is considerable difference of opinion concerning the nature of palisade ending function. Palisade endings in EOMs were examined in cats to test whether they display motor or sensory characteristics. We injected an anterograde tracer into the oculomotor or abducens nuclei and combined tracer visualization with immunohistochemistry and -bungarotoxin staining. Employing immunohistochemistry, we performed molecular analyses of palisade endings and trigeminal ganglia to determine whether cat palisade endings are a cholinergic trigeminal projection. We confirmed that palisade endings are cholinergic and showed, for the first time, that they, like extraocular motoneurons, are also immunoreactive for calcitonin gene-related peptide. Following tracer injection into the EOM nuclei, we observed tracer-positive palisade endings that exhibited choline acetyl transferase immunoreactivity. The tracer-positive nerve fibers supplying palisade endings also established motor terminals along the muscle fibers, as demonstrated by -bungarotoxin. Neither the trigeminal ganglion nor the ophthalmic branch of the trigeminal nerve contained cholinergic elements. This study confirms that palisade endings originate in the EOM motor nuclei and further indicates that they are extensions of the axons supplying the muscle fiber related to the palisade. The present work excludes the possibility that they receive cholinergic trigeminal projections. These findings call into doubt the proposed proprioceptive function of palisade endings.
AB - Palisade endings are nerve specializations found in the extraocular muscles (EOMs) of mammals, including primates. They have long been postulated to be proprioceptors. It was recently demonstrated that palisade endings are cholinergic and that in monkeys they originate from the EOM motor nuclei. Nevertheless, there is considerable difference of opinion concerning the nature of palisade ending function. Palisade endings in EOMs were examined in cats to test whether they display motor or sensory characteristics. We injected an anterograde tracer into the oculomotor or abducens nuclei and combined tracer visualization with immunohistochemistry and -bungarotoxin staining. Employing immunohistochemistry, we performed molecular analyses of palisade endings and trigeminal ganglia to determine whether cat palisade endings are a cholinergic trigeminal projection. We confirmed that palisade endings are cholinergic and showed, for the first time, that they, like extraocular motoneurons, are also immunoreactive for calcitonin gene-related peptide. Following tracer injection into the EOM nuclei, we observed tracer-positive palisade endings that exhibited choline acetyl transferase immunoreactivity. The tracer-positive nerve fibers supplying palisade endings also established motor terminals along the muscle fibers, as demonstrated by -bungarotoxin. Neither the trigeminal ganglion nor the ophthalmic branch of the trigeminal nerve contained cholinergic elements. This study confirms that palisade endings originate in the EOM motor nuclei and further indicates that they are extensions of the axons supplying the muscle fiber related to the palisade. The present work excludes the possibility that they receive cholinergic trigeminal projections. These findings call into doubt the proposed proprioceptive function of palisade endings.
KW - Abducens Nerve/cytology
KW - Animals
KW - Axons/physiology
KW - Bungarotoxins
KW - Calcitonin Gene-Related Peptide/metabolism
KW - Cats
KW - Choline O-Acetyltransferase/metabolism
KW - Fluorescent Antibody Technique
KW - Immunohistochemistry
KW - Motor Neurons/physiology
KW - Muscle Fibers, Skeletal/physiology
KW - Nerve Endings/physiology
KW - Oculomotor Muscles/innervation
KW - Parasympathetic Nervous System/physiology
KW - Proprioception/physiology
KW - Trigeminal Nerve/cytology
UR - https://www.scopus.com/pages/publications/84873629438
U2 - 10.1523/JNEUROSCI.4116-12.2013
DO - 10.1523/JNEUROSCI.4116-12.2013
M3 - Journal article
C2 - 23407938
SN - 0270-6474
VL - 33
SP - 2784
EP - 2793
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 7
ER -