[Structural modifications of the thoracic region of vagus and sympathetic trunk ganglia after exposure to gravitational overloads].

The aim of this work was the complex study of structural modifications in the anterior thoracic ganglia of the sympathetic trunk and in thoracic region of vagus after acute and chronic exposure to gravitational overloads (GO). The study was carried out in 28 albino outbred male rats aged 8-21 weeks. Animals of group I (acute exposure) were rotated in the centrifuge during one day (3 rotations with 2 20-min breaks; total exposure duration was equal to 31 min. Animals of group II (chronic exposure) were treated intermittently during 2-weeks-long periods for 13 weeks; total exposure duration was equal to 20 hours 9 min. Gravitation was applied in cranio-caudal direction with the overload of 4-6 gravitational units. Intact rats served as a control. Material was studied using histological, electron microscopic and morphometric methods. The study of the sympathetic trunk and thoracic ganglia following acute GO have revealed mainly the reactive and reversible changes, probably caused by the appearance of an afferent impulsation of unusual intensity and combination, which is one of the reasons of the disturbances, observed after rotation. Following chronic GO, destructive and compensatory-adaptive changes prevailed; these were characterized by the mitochondrial cristae destruction, vacuolization of neuronal cytoplasm, destruction of interneuronal synapses. These changes, were probably, the result of hypoxia leading to the development of interneuronal synaptic block in sympathetic ganglia. The structural modifications described are indicative of the involvement of both sympathetic and parasympathetic parts of the autonomic nervous system in the response to acute and chronic GO, suggesting the generalization of the adaptation processes in the autonomic nervous system after GO.