Koshkin O. Age features of morphofunctional characteristics of masticatory muscles in the normal condition and experimental diabetes mellitus

130 white 2-month-old laboratory male rats (weighing 75-90 g) and 6-month-old rats (160-180 g) were used for the study; all experimental animals were divided into 2 groups. The first group included 20 intact animals (10 rats of different age groups) which did not undergo any manipulations. The second group was divided into 2 subgroups: 2a – with simulated SIDM (35 rats of different ages), 2b – control (25 two-month-age rats and 15 six-month-age rats). SIDM was simulated by a single intraperitoneal injection of streptozotocin at a rate of 7 mg/100g body weight to 2-month-old rats and 6 mg/100g body weight to 6-month-old rats. Sampling was performed on the 14th, 28th, 42th, 56th and 70th days of the experiment. For the first time, the features of postnatal morphogenesis of the masticatory and temporal muscles have been established with the help of complex research methods. It’s proved for the first time that in the temporal muscle the area of neuromuscular endings (NMEs) and patterns of branches of terminal branches of axons are probably larger than the corresponding values of the masticatory muscle in rats of different age groups and depend on the size of muscle fibers (MFs), which is confirmed by the revealed direct proportional correlation between the areas of MFs and NMEs. For the first time, it’s shown that individual MFs of the studied muscles of 2-month-old animals have polyneuron innervation, while in 6-month-old rats it is only mononeuronal. The research priority is in the fact that for the first time the age features of structural rearrangement of angio- and myeloarchitectonics of temporal and masticatory muscles in case of SIDM and changes in their bioelectrical activity are established, which reveal the main pathomorphological mechanisms of diabetic myopathy taking into account the chronobiological aspect of the stages of diabetes mellitus. For the first time, on the basis of complex histological, histochemical, electron microscopic, morphometric, electromyographic and statistical research methods the new data were obtained, which in the dynamics of morphofunctional changes of the temporal and masticatory muscles in case of SIDM in 6-month-old rats allowed to allocate two stages: reactive-compensatory (14th -28th days) and atrophic-destructive (42th -70th days); and in 2-month-old rats – reactive-hypotrophic (14th -42th days) and compensatory (56th -70th days). Key words: masticatory muscle, temporal muscle, neuromuscular endings, hemomicrocirculatory flow, streptozotocin-induced diabetes mellitus, electromyography. Branch-Medicine.