Morphofunctional structure of masseter neuromuscular connections in rats in norm
DOI:
https://doi.org/10.11603/2311-9624.2017.3.8033Keywords:
masseter, neuromuscular junction, neuromuscular synapse.Abstract
A number of studies indicate that synaptoarchitectonics in mature skeletal muscles is characterized by considerable variability and largely depends on the function of the muscle and the phenotype of muscle fi bers. However, quantitative and qualitative morphological studies of neuromuscular synapses of the rat chewing muscle remained outside the fi eld of view of the researchers.
The aim of the study – to establish the features of the morphofunctional structure of the neuromuscular junction of the rat’s masseter in norm.
Materials and Methods. The material for the study was the masticatory muscles of 10 mature male rats of the Wistar line (body weight 180–200 g). To detect neuromuscular junctions, the chewing muscles were fi xed for 25–30 days in 12 % neutral formalin. The material was washed and made a cut of 30–40 μm thick in a cryostat, which were processed by the Bilshowski-Gros method. For electronic research, the sampling was carried out according to generally accepted rules. Pieces of muscle fi bers were fi xed in a 2 % solution of osmium tetroxides, and contrasting according to the conventional method. Stimulation and interference electroneuromyography was performed on Neuro-EMG-Micro computer Neur EMG micro microcomputer manufactured by Neurosoft Company (Russia), which has low noise level, high sensitivity (10–500 μV / cm) and resistance to distortion. Computer processing of data was carried out using statistical package Stat.Soft.Inc; Tulsa, OK, USA; Statistica 6.
Results and Discussion. In the masticatory muscle, neuromuscular junctions have their synaptoarchitectonics, which are characterized by: scouting of the motor axon, length and width of the active zones, the number and size of synaptic folds, the number of neurolematocytes, the peculiarity of the structure of the spinal-protective membrane. The area of the neuromuscular junction is (385.74 ± 16.63) μm 2. The neuromuscular junction includes several neuromuscular synapses, which have the following quantitative characteristics: area – (6.23 ± 1.03) μm2, the length of the synaptic junction is (2.56 ± 0.52) μm, the number of folds of the synaptic membrane is 8.6 ± 0.69, the distance between the folds is – (0.35 ± 0.002) μm, the length of the individual fold is (3.31 ± 0.03), the number of synaptic vesicles is (172.69 ± 16.03).
Conclusions. Electro neuromyographic studies of masticatory muscles indicate the correct direction of nerve impulse transmission, high amplitude characteristics of excitation transfer and M-response in case of single stimulation.
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