[Nitric oxide is involved in the protective effects of short-term adaptaion to hypoxia in the course of stress-induced disorders in Krushinsky-Molodkina rats].

A possible involvement of nitric oxide in the protective effect of short-term adaptation of Krushinsky-Molodkina rats to mild hypoxia simulating 5000 m above sea level was studied. Nitric oxide proved to have a considerable protective effect on stress-induced disorders in Krushinsky-Molodkina rats as demonstrated using NO-synthase inhibitors and NO monitoring by electron spin resonance under different experimental conditions.

[Reduction of erythrocyte deformability in Krushinskii-Molodkina rats in acute hemorrhagic cerebrovascular circulation disorders].

The ability of erythrocytes to change their shapes in the shear flow under acute strokes of hemorrhagic type in rats of the Krushinsky-Molodkina line was studied. The rigidity of membranes and the internal viscosity of erythrocytes were investigated by the laser diffraction method. The method consists in obtaining diffraction images from a thin layer of a dilute suspension of erythrocytes moving in the shear flow and subsequent computer processing of these images. It was shown that strokes of hemorrhagical type in rats of the Krushinsky-Molodkina line cause a reduction in the ability of erythrocytes to change theirs shapes.

[Antistress and angioprotective influence of nitric oxide in epilepsy-prone rats of Krushinskii-Molodkina strain].

In rats of Krushinsky-Molodkina strain (KMR), the audiogenic stress induced epileptiform seizure and development of acute disturbances of cerebral circulation of hemorrhagic nature. The inhibitor of NO-synthase (L-NNA) increased the severity of clinical symptoms, mortality, and the intensity of intracranial hemorrhages. In contrast, L-arginine elevated the resistance of KMRs to acoustic stress. The intensity of nitrergic innervation was analyzed in preparations of the middle cerebral artery with the use of histochemical NADPH-diaphorase staining. In preparations of control KMRs, a net of NADPH-positive perivascular nerve fibers was found, while in experimental KMRs, in an hour after sound stimulation, such fibers practically were not revealed. Preliminary exposure of KMRs in hypoxic conditions (1 hour in hypobaric chamber at simulated altitude of 5000 m above the sea level) decreased the development of stress lesions. The protective effect of hypoxic training disappeared after the administration of NO-synthase inhibitor (L-NNA). The study demonstrated participation of nitric oxide (NO) in adaptive reactions of cerebral hemodynamics linked with the significant increase of cerebral blood flow.

[Effect of two-week tail suspension on the reactivity of rat's cerebral vessels].

Reactivity of the cerebral vessels feeding two different brain regions was studied in rats after the hind limb unloading during two-wk tail-suspension. The basilar and middle cerebral arteries were isolated and perfused with a steady flow of the Krebs solution. Constriction responses to serotonin (10(8)-10(5) M) and high-K+ solution (100 mM) and dilatation responses to the beta-adrenoceptor agonist isoproterenol (10(8)-3 x 10(6) M) were evaluated. Tail suspension had no effect on the reactivity of the middle cerebral artery. The basilar artery reaction to K+ and isoproterenol remained unchanged compare to the control, whereas the reaction to serotonin was augmented significantly. Therefore, regional differences in the cerebral vessels reactivity were observed in rats after two weeks of tail suspension.

[Semax prevents elevation of nitric oxide generation caused by incomplete global ischemia in the rat brain]. / Semaks preduprezhdaet povyshenie generatsii oksida azota v mozge krys, obuslovlennoe nepolnoi global'noi ishemiei.

A twofold increase in the nitric oxide (NO) production and a moderate increase in the content of secondary products of lipid peroxidation was observed in Wistar rats with incomplete global ischemia model induced by the bilateral occlusion of common carotid arteries. A clear correlation was observed between the NO content in the rat brain and the level of neurological disturbance manifestations in the ischemized animals. The synthetic peptide semax (a fragment of ACTH4-7 Pro-Gly-Pro) in a dose of 0.3 mg/kg prevented from the development of both neurological disturbances and excess NO production in the rat brain cortex.

[Changes in reactivity of the middle cerebral artery caused by cerebral circulation disturbances of ischemic and hemorrhagic types in rats]. / Izmeneniia reaktivnosti srednei mozgovoi arterii krysy, vyzvannye narusheniiami mozgovogo krovoobrashcheniia ishemicheskogo i gemorragicheskogo tipov.

Reactivity of the middle cerebral artery (MCA) to serotonin was attenuated in vitro in vessels taken from rats following an audiogenic stress. The MCA reactivity to endothelin remained unchanged. Chronic cerebral ischemia diminished the 5-HT-induced contraction and the contractile responses to endothelin were enhanced. Preliminary hypoxic adaptation decreased the artery sensitivity to endothelin in ischemic animals. The findings suggest that a progressing ischemia may involve changes in reactivity of cerebral vessels whereupon hypoxic adaptation may prove to be protecting the brain from ischemia development.