Neuronal Syncytia in the Enteric Nervous System of the Felis Catus

Abstract

Syncytial connections between neurites were found using electron microscopy in the nervous system of cats, young pigs, as well as in the culture of mollusk ganglia cells. The possibility of detecting neural syncytia using the method of the unmasking of digital images of arborizations of interneuronal connections in the nervous tissue of the brain was established, but this method was not used to study of the enteric nervous system. The aim of the study was to analyze the submucosal and intermuscular autonomic nerve plexuses of the intestine of the domestic cat (Felis catus) by method of the unmasking of digital images. The material for the study was preparations of the small and large intestines. All manipulations with animals were carried out in compliance with Directive 2010/63/EU of the European Parliament and of the Council of the European Union on the protection of animals used for scientific aims. The experiments were carried out on mature outbred cats (n=45). To obtain preparations, the intestinal vessels of experimental animals were sequentially perfused with solutions of barium hydroxide, then silver nitrate, and hydroquinone. After perfusion, intestinal preparations were taken and fixed. The obtained histological preparations (including ultramicroscopic ones) were studied by the method of unmasking of digital images (of the downscaling of the image resolution). As a result of the study, numerous distant syncytial anastomoses connecting the bodies of neurocytes of all types of Dogiel cells were revealed for the first time, and their properties were established. Widespread multiple morphological mono- and polyvalent ring syncytial structures were found. Their supposed function is the opposite direction of electric and axoplasmic flow. An in vivo feature of the reflex syncytial apparatus of the enteric nervous system is the formation of multi-tiered closed loop-like contacts of nerve fibers and type II Dogiel cells with pronounced local and diffuse receptor branches. Thus, a characteristic feature of the enteric nervous system is the presence of multicellular connections of neurocytes in the form of a network of distant syncytial anastomoses. These anastomoses are real proof of the reticular principle of the structural organization of the autonomic plexuses of the enteric nervous system and the reticular concept in general.