[Morphofunctional changes in the vascular system of the rabbit brain in rocking during anti-orthostatic position and administration of dimephosphon].

It was demonstrated by experiment that exposure of non-anesthetized rabbits to rocking in the head-down position at -30 degrees led to acidosis, hypoxemia and hypercapnia, changes in impedance components that were suggestive of water imbalance in the cerebral tissue, paralytic dilation of microcirculation vessels, subarachnoidal hemorrhages, hyaline thrombi, stasis and sludge-syndrome, small perivascular extravasates in different brain compartments, marked perivascular and pericellular edema. Pretreatment with dimephosphone prevented or attenuated significantly acidosis, water imbalance, and pathomorphological disorders in the vascular system, nervous and glial elements of the brain of the rabbits examined.

[Changes in the cerebral hemodynamics under the influence of piracetam and fenibut during motion sickness].

In the experiments on conscious rabbits with the electrodes implanted in the brain it was found by the methods of hydrogen clearance and polarography that piracetam (50 and 500 mg/kg) and phenibut (50 mg/kg) induced a decrease of the local blood flow in the cortex of the frontal, temporal and occipital regions and the total cerebral blood flow. The administration of the drugs before tilting prevents the occurrence of vasodilatation in the brain and results in a decrease of the blood flow in the cortex and in the confluence of the cerebral venous sinuses that is thought to be connected with the mechanism of an increase of the vestibular stability under the influence of GABA derivatives.

Role of cholinergic mechanisms in alterations of rabbit brain functional activity during sea-sickness.

Using the hydrogen-clearance method in chronic experiments on alert rabbits, we investigated the dynamics of changes in local and total cerebral blood-flow, oxygen pressure, bioelectrical activity of the motor, auditory, and visual zones of the cerebral cortex, the heart rate during sea-sickness and the effect of the cholinolytic scopolamine upon changes in these indices. It was found that scopolamine affects the character and direction of changes in both local and overall blood flow in the brain during sea-sickness. Scopolamine does not substantially alter oxygen pressure in the cortical structure of the brain and does not eliminate brachycardia arising during sea-sickness.

[The effect of pyridoxine on the cerebral hemodynamics in vestibular disorders].

By means of hydrogen clearance on conscious rabbits with implanted platinum electrodes it was established that pyridoxine (1 and 10 mg/kg) used against the background of sea sickness decreased the dilatational reaction of the cerebral vessels occurring during the stimulation of the vestibular apparatus, reduced the blood supply to the cerebral hemispheres with insignificant changes of oxygen tension in the cortical structures, relieved acidosis and hypoxemia developing during sickness in the orthostatic position, increased oxygenation of the arterial blood without influencing significantly pathomorphological shifts in the brain tissue.

[The cerebrovascular effects of motion sickness].

In rabbits with implanted electrodes, a diminished reactivity of vascular vessels to functional tests of physical and chemical nature was revealed although the level of cerebral blood flow generally increased. This suggests a reduction of compensatory capacity of the brain circulation system which can result in a change of the brain tissue water balance under the effects leading to an alteration of cerebral outflow and sometimes accompanying seasickness. This was corroborated by the evidence on a change in cerebral tissue impedance under the combined effect of antiorthostatism and seasickness, as well as by the evidence on dynamics of cerebral rheogram pulse waves.