D. P. Dvoretskii

Influence of High Blood Pressure on Microcirculation in Cerebral Cortex of Young Rats

We studied the density and structure of the microvascular network of the pia mater, the blood flow rate and oxygen saturation in the sensorimotor cortex of young spontaneously hypertensive rats (SHR). The density of the microvascular network in hypertensive animals was by ~1.4 times lower than in normotensive Wistar-Kyoto rats (control) and arteriolar bed density was lower by ~1.9 times. The blood flow rate in tissue and oxygen saturation in the sensorimotor cortex in SHR rats were significantly lower than in control animals.

Age-related changes of microcirculation in pial blood vessels of the sensorimotor cortex of the rat brain

We studied the density of the entire microvascular network and arterioles in the pia mater of the sensorimotor cortex in rats of different ages. The responses of pial arterioles to noradrenaline and acetylcholine chloride were also studied. Our results showed that the density of the microvascular network and reactivity of arterioles in the pia mater did not significantly change before the age of 12 months. At the age of 22–24 months, the density of the entire microvascular network was decreased by 1.7 times; the density of arterioles was decreased by 1.2 times. The contractility of pial arterioles did not significantly change during the rat lifespan; however, their ability to dilate became poorer with age. Exploratory behavior was impaired by the age of 22–24 months: the number of events in the open-field test was decreased by 1.5–2.3 times in comparison with young animals.

Effect of Low-Intensity Laser Radiation of the Red Spectrum on Some Properties of Erythrocytes in Wistar Rats

Laser radiation of different power had various effects on the properties of erythrocytes. An increase in the radiation power from 2.2 to 25 mW/cm2 was accompanied by a decrease in the erythrocyte sedimentation rate and an increase in erythrocyte filtration index. Radiation of 50 mW/cm2 induced abnormal erythrocyte aggregation. Increasing the time of irradiation at power intensity of 2.2 mW/cm2 did not potentiate its effect on the blood.

Neurogenic Vasoconstriction of Pial Arterial Vessels of Various Branching Orders in Normotensive and Spontaneously Hypertensive Rats

Intravital television microscopy was employed to study the reaction of pial arteries in normotensive and spontaneously hypertensive rats to stimulation of the superior cervical ganglion. The amplitude of constrictor response was similar in WKY and SHR animals. Under conditions of normal arterial pressure and arterial hypertension, the maximum constrictor effect was attained due to equal involvement of the arteries from all generations in the normotensive rats and predominant constriction of the precortical arterioles in SHR animals.

Changes in Cerebral Blood Flow in the Postischemic Period

Experiments on Wistar rats showed that blood flow in the cortex and subcortical brain structures was not completely restored within 21 days after transient ischemia caused by bilateral carotid artery occlusion with controlled hypotension. After 7 days of reinfusion, the end-diastolic blood flow velocity increases with simultaneous decrease in pulsation index, which indicates the decrease in peripheral vascular resistance. During the following 14 days, peripheral blood resistance increases, as was seen from the increased peak systolic blood flow velocity, mean blood flow velocity over the heart cycle, and pulsation index. These changes are likely a delayed manifestation of ischemic reperfusion injury to brain microvessels (no-reflow phenomenon) and are determined by changes in blood rheologiy and pial vessel lumen.

Differences in adrenoreception in the microcirculatory bed of the pia mater in normotensive and spontaneously hypertensive rats

Adrenoceptors in pial vascular bed of normotensive Wistar-Kyoto rats are distributed unevenly during stimulation of the superior cervical ganglion, their density was maximum in the 5th-generation arteries. In spontaneously hypertensive rats (SHR) the density of adrenoceptor is lower than in normotensive rats and their number is maximum in the 1st-generation arteries.

Effect of Transplantation of Mesenchymal Stem Cells on the Density of Pial Microvascular Network in Spontaneously Hypertensive Rats of Different Age

Using a TV device for studying microcirculation (×40), we analyzed the density of the whole microvascular network and the density of arterioles in the pia mater of the sensorimotor cortex in SHR rats of different ages (3-4 and 12 months) after intracerebral transplantation of human mesenchymal stem cells. We found that the density of pial microvascular network in SHR rats receiving transplantation of human mesenchymal stem cells increased to a level observed in young Wistar-Kyoto rats.

Comparative Analysis of the Potentiating Action of Noradrenaline on Neurogenic Vasoconstriction Diminished by Various Factors

In vitro experiments on segments of the tail artery of young Wistar rats addressed the influence of noradrenaline (0.03–1.0 μM) on neurogenic constriction of these segments evoked by electric field stimulation in conditions of a reduction in perfusate pH from 7.4 to 6.6 or perfusate temperature from 36 to 25°C. Noradrenaline was found to potentiate neurogenic vasoconstriction after its suppression by a decrease in solution temperature or pH. In conditions of identical decreases in neurogenic vasoconstriction, the potentiating actions of low noradrenaline concentrations were most marked after cold-induced decreases, while the potentiating actions of high concentrations were most marked after acidosis-induced decreases. Noradrenaline (0.1 μM) was identically effective in both cases. The possible physiological significance of these vascular reactions is discussed.

Postischemic Responsiveness of Pial Vessels to Hypercapnia

Reactions of pial vessels to hypercapnia were studied in Wistar rats one week after global cerebral ischemia. In ischemic rats, the responsiveness of pial vessels to hypercapnia was diminished, which promoted a decrease in cerebral perfusion reserve. Changes in vascular responsiveness in the arterial and venous subdivisions of the vascular bed were observed and probably resulted from ischemia-provoked down-regulation of the vascular tone.

Effects of Intracerebral Transplantation of Mesenchymal Stem Cells on the Density of the Microvascular Network of the Pia Mater of the Rat Cerebral Cortex

A television apparatus designed for analysis of the microcirculation (at magnifications of × 30–160) was used to investigate the density of the microvascular network in the pia mater of the rat sensorimotor cortex after intracerebral transplantation of mesenchymal stem cells or (as controls) stem cell cultivation medium or physiological saline. The results showed that intracerebral transplantation did not alter the density of the microvascular network in the pia mater of the ipsilateral hemisphere, while there were no changes in either hemisphere in the control group. Transplantation of mesenchymal stem cells led to increases in the density of the microvascular network of the pia mater of the contralateral hemisphere by a factor of 1.8 as compared with control animals; the number of arterioles in this zone was 2.5 times greater than that in intact rats.