Palisade Endings Have an Exocytotic Machinery But Lack Acetylcholine Receptors and Distinct Acetylcholinesterase Activity

Blumer, Roland; Streicher, Johannes; Carrero-Rojas, Génova; Calvo, Paula M.; Cruz, Rosa R. de la; Pastor, Ángel M.

doi:10.1167/iovs.61.14.31

Cited by 9 publications

(18 citation statements)

References 52 publications

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“…There is indication from the literature that palisade endings are expansions of motoneuron axons that establish multiple en grappe motor terminals alongside muscle fibers. 16 , 18 Motoneurons that establish multiple motor terminals are termed MIF motoneurons as opposed to SIF motoneurons that establish a single motor endplate. 32 We looked for palisade endings associated with en grappe motor terminals on the control and injected sides.…”

Section: Resultsmentioning

confidence: 99%

“…A more detailed description of immunolabeling of EOM whole-mounts is provided elsewhere. 16 For negative controls, primary antibodies were omitted, and secondary antibodies were used alone. In all cases, the omission of the primary antibodies resulted in a complete lack of immunostaining.…”

Section: Methodsmentioning

confidence: 99%

“… 6 Structurally, palisade endings have similarities to sensory Golgi tendon organs, but molecular and connectional features indicate that they are more compatible with motor structures. Specifically, palisade endings are cholinergic, 13 – 15 express key proteins involved in neurotransmitter (acetylcholine) release, 16 and originate from the EOM motor nuclei, most likely from neurons whose axons establish multiple motor endings (en grappe motor terminals) along the so-called multiply innervated muscle fibers (MIFs). 17 , 18 Because sensory and motor features coexist in palisade endings, their function is still elusive.…”

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confidence: 99%

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Eye Movements But Not Vision Drive the Development of Palisade Endings

Carrero-Rojas

Calvo

Lischka

et al. 2022

Invest. Ophthalmol. Vis. Sci.

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Purpose To test whether visual experience and/or eye movements drive the postnatal development of palisade endings in extraocular muscles. Methods In three newborn cats, the right eye was covered until 30 days from postnatal (P) day 7 (before opening their eyes), and in three cats both eyes were covered until 45 days, also from P7. To block eye movements, another seven cats received a retrobulbar injection of botulinum neurotoxin A (BoNT-A) into the left orbit at birth and survived for 45 days (three cats) and 95 days (four cats). The distal third of the rectus muscles containing the palisade endings was used for whole-mount preparation and triple-fluorescence labeling with anti-neurofilament along with (1) anti-synaptophysin and phalloidin or (2) anti-growth associated protein 43 (GAP43) and phalloidin. Immunolabeled specimens were analyzed in the confocal laser scanning microscope. Results After unilateral and bilateral dark rearing, palisade endings were qualitatively and quantitatively equal to those from age-matched controls. After BoNT-A induced eye immobilization for 45 or 95 days, palisade endings were absent in the superior rectus and lateral rectus muscles and only present in the inferior rectus and medial rectus muscle. These BoNT-A–treated palisade endings were rudimentary and reduced in number, and the expression of the neuronal developmental protein GAP43 was significantly reduced. Conclusions This study demonstrates that eye immobilization, but not visual deprivation, affects palisade ending development. Palisade endings develop in the first month of life, and the present findings indicate that, during this time window, palisade endings are prone to oculomotor perturbations.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Eye Movements But Not Vision Drive the Development of Palisade Endings

Carrero-Rojas

Calvo

Lischka

et al. 2022

Invest. Ophthalmol. Vis. Sci.

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“…The muscle fibers associated with palisade endings are the MIFs of the global layer of extraocular muscles, which are characterized by the presence of en grappe nerve endings along their length (Ruskell, 1978;Alvarado-Mallart and Pinçon-Raymond, 1979). We have previously shown that palisade endings are in continuity with MIF motoneuronal axons (Zimmermann et al, 2013;Blumer et al, 2020), thereby en grappe terminals and palisade endings arise both from the same MIF motoneuron. Other authors, however, have hypothesized that palisade endings arise from sensory neurons located in the oculomotor nucleus, which in turn would synapse with MIF motoneurons, suggesting in this way a proprioceptive reflex (Lienbacher and Horn, 2012).…”

Section: Relationship Between Mif Motoneurons and Palisade Endingsmentioning

confidence: 99%

“…Palisade endings were described as sensory structures based on their morphology (Ruskell, 1978;Alvarado-Mallart and Pinçon-Raymond, 1979). Nonetheless, their function is under debate as connectional and molecular characteristics suggest a motor role, that is, palisade endings are cholinergic, are traced from the oculomotor nuclei, contain key proteins of the exocytotic machinery but lack, however, postsynaptic nicotinic acetylcholine receptors and have little, if any, extracellular acetylcholinesterase (Blumer et al, 2009(Blumer et al, , 2016(Blumer et al, , 2020Zimmermann et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

MIF versus SIF Motoneurons, What Are Their Respective Contribution in the Oculomotor Medial Rectus Pool?

et al. 2021

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Multiply-innervated muscle fibers (MIFs) are peculiar to the extraocular muscles as they are non-twitch but produce a slow build up in tension on repetitive stimulation. The motoneurons innervating MIFs establish en grappe terminals along the entire length of the fiber, instead of the typical en plaque terminals that singly-innervated muscle fibers (SIFs) motoneurons establish around the muscle belly. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. We aimed to discern the function of MIF motoneurons by recording medial rectus motoneurons of the oculomotor nucleus. Single-unit recordings in awake cats demonstrated that electrophysiologically-identified medial rectus MIF motoneurons participated in different types of eye movements, including fixations, rapid eye movements or saccades, convergences, and the slow and fast phases of the vestibulo-ocular nystagmus, the same as SIF motoneurons did. However, MIF medial rectus motoneurons presented lower firing frequencies, were recruited earlier and showed lower eye position (EP) and eye velocity (EV) sensitivities than SIF motoneurons. MIF medial rectus motoneurons were also smaller, had longer antidromic latencies and a lower synaptic coverage than SIF motoneurons. Peristimulus time histograms (PSTHs) revealed that electrical stimulation to the myotendinous junction, where palisade endings are located, did not recurrently affect the firing probability of medial rectus motoneurons. Therefore, we conclude there is no division of labor between MIF and SIF motoneurons based on the type of eye movement they subserve.

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