Related Experiment Video
Updated: Jun 5, 2026

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in Aplysia californica
Published on: March 25, 2013
Do palisade endings in extraocular muscles arise from neurons in the motor nuclei?
Karoline Lienbacher1, Michael Mustari, Howard S Ying
1Institute of Anatomy I, Ludwig-Maximilian University of Munich, Munich, Germany.
Purpose:
The purpose of this study was to localize the cell bodies of palisade endings that are associated with the myotendinous junctions of the extraocular muscles.
Methods:
Rhesus monkeys received tract-tracer injections (tetramethylrhodamine dextran [TMR-DA] or choleratoxin subunit B [CTB]) into the oculomotor and trochlear nuclei, which contain the motoneurons of extraocular muscles. All extraocular muscles were processed for the combined immunocytochemical detection of the tracer and SNAP-25 or synaptophysin for the visualization of the complete muscle innervation.
Results:
In all muscles--except the lateral rectus--en plaque and en grappe motor endings, but also palisade endings, were anterogradely labeled. In addition a few tracer-labeled tendon organs were found. One group of tracer-negative nerve fibers was identified as thin tyrosine hydroxylase-positive sympathetic fibers, and a second less numerous group of tracer-negative fibers may originate from the trigeminal ganglia. No cellular or terminal tracer labeling was present within the mesencephalic trigeminal nucleus or the trigeminal ganglia.
Conclusions:
These results confirm those of earlier studies and furthermore suggest that the somata of palisade endings are located close to the extraocular motor nuclei--in this case, probably within the C and S groups around the periphery of the oculomotor nucleus. The multiple en grappe endings have also been shown to arise from these cells groups, but it is not possible to distinguish different populations in these experiments.
Related Concept Videos
Muscles of the Eye
Extraocular Muscles
The six extraocular muscles surround the eyeball and control its movements. They are responsible for a wide range of eye motions, including looking up, down, left, right, and rotating...
Cranial Part of Parasympathetic Division
The vagus nerve (cranial nerve X) alone accounts for approximately 75...
Accessory Structures of the Eye
Cranial Nerves: Types Part I
Olfactory Nerve (Cranial Nerve I)
The olfactory nerve, or cranial nerve I, is unique as it is purely sensory and dedicated to the sense of smell. This nerve originates in the olfactory epithelium of the...
The Neuromuscular Junction
Brainstem
The Midbrain
The midbrain is located beneath the diencephalon and connects the cerebrum with the lower parts of the brain. The cerebral peduncles are prominent midbrain structures that house the...

