Organization of acetylcholine-containing structures in the cranial motor nuclei of the rhombencephalon of the pig

We explored the immunoreactivity of choline acetyltransferase (ChAT) in the cranial nerve motor nuclei of the porcine rhombencephalon to reveal the cholinergic nature of these regions. In our experiments we used an immunohistochemical method for the visualization of all acetylcholine-containing structures. All studied motor nuclei contained ChAT-positive cell bodies and fibres, but the intensity of staining differed between the nuclei. Furthermore, characteristic ChAT-immunoreactive bouton-like structures, which are known to be synaptic terminals of the cholinergic system, were observed in the borders of all studied regions. The localization of ChAT-positive “boutons” in the neuropil of the examined nuclei and their proximity to stained perikarya allowed us to differentiate two groups of motor nuclei in the rhombencephalon of the pig: (a) Nuclei containing ChAT-positive bouton-like structures dispersed in the neuropil, often establishing contacts with the stained cell bodies – motor trigeminal, abducent, facial, ambiguous and hypoglossal nuclei. (b) Nuclei in which characteristic boutons were dispersed among the ChAT-positive cells, but were devoid of any contact with perikarya – dorsal motor nucleus of the vagus nerve. These results provide new data on the porcine central nervous system and could be useful in further experiments on amyotrophic lateral sclerosis (ALS) – the disease that results in the progressive degeneration of motoneurons in the brain and spinal cord.