A comprehensive spectral analysis of the vibrational components of the myogenic, neurogenic, and endothelial components of microvascular tone was performed and the dynamics of oxygen transport in the cerebral cortex of rats aged 4, 18, and 23 months was evaluated using the method of laser Doppler flowmetry and tissue optical oximetry. Regional differences in age-related changes in the regulatory mechanisms of microcirculation and the effectiveness of tissue oxygen extraction have been identified. It was found that at the age of 18 months, microcirculatory changes are observed in the frontal and parietal cortex and manifest themselves as a decrease in sympathetic regulation of microcirculation, a decrease in precapillary myogenic resistance, vasodilation, and an increase in the contribution of the capillary link to microcirculation. In the parietal cortex, these changes contribute to the activation of tissue oxidative metabolism and increased oxygen consumption from the flowing blood. With further aging, microvascular endothelial dysfunction develops and the contribution of the endothelial component to the overall perfusion level of all cortical regions decreases. These disorders in 23-month-old rats are accompanied by an increase in the contribution of sympathetic regulation of microcirculation in the frontal cortex, a decrease in the contribution of the capillary link to microcirculation in the occipital region and the development of stagnant processes in the venous region of the microcirculatory bed of the parietal cortex, reducing the effectiveness of tissue oxygen extraction from the blood.

BACKGROUND: In the treatment of diabetes mellitus (DM) for a persistent reduction in blood glucose levels it was widely used glibenclamide — a KATP channels blocker. However, its effects on cerebral circulation have been studied very little. A decrease in the functional activity of KATP channels due to their blocking by glibenclamide against the background of developed endothelial dysfunction may lead to impaired cerebral circulation (especially at the microcirculatory level) and promote remodeling of the vascular network.AIM: To evaluate the effect of glibenclamide on the reactivity of cerebral arteries in rats with streptozotocin-induced diabetes mellitus (STZ-T2DM).TASKS: 1. To study changes in the functional state of KATP channels of pial arteries in STZ-T2DM. 2. To evaluate the effect of glibenclamide on the participation of KATP channels in the formation of basal tone and endothelium-dependent dilatation of pial arteries.MATERIALS AND METHODS: The study was performed on 54 male Sprague Dawley rats. Streptozotocin-induced diabetes mellitus (STZ-T2DM) was modeled by keeping animals on a high-fat diet and administering streptozocin (35 mg/kg). Using an installation for intravital study of pial vessels reactivity, 3 months from the beginning of the experiment, the diameter of the arteries was measured when the brain surface was irrigated with Krebs-Henseleit solution, acetylcholine, glibenclamide, pinacidil and acetylcholine against the background of the action of glibenclamide or pinacidil.RESULTS: With modeling STZ-T2DM, rats developed glucose tolerance and insulin resistance. Compared to control animals, body weight was 1,3 times higher, the percentage of visceral fat was 3 times higher, and the blood glucose level was 3,2 times higher. It was shown that in STZ-T2DM the number of pial artery constrictions under the action of glibenclamide decreased by 1,3 — 1,9 times compared to intact rats. Glibenclamide did not block endothelium-dependent dilation.CONCLUSION: In rats with streptozotocin diabetes, KATP channels take part in the formation of the basal tone of the pial arteries, but the contribution of these channels is reduced on average by 1.5 times compared to healthy rats.The use of glibenclamide in STZ-T2DM does not affect endothelium-dependent dilatation of cerebral arteries.

This study aims to examine the efficiency of intravenous transplantation of human mesenchymal stem cells (hMSCs) performed 7 days after cerebral ischemia/reperfusion (I/R) for recovery of the functional activity of KATP-channels of cerebral arteries. Using a device for intravital visualization of pial vessels, the reaction of arteries to the KATP-channel blocker glibenclamide (GB), the activator of the same channels of pinacidil (PI), acetylcholine (ACh), and ACh against a background of GB action (ACh/GB) 14 and 21 days after I/R and intravenous hMSC transplantation performed 7 days after ischemic exposure. On exposure to GB 14 days after I/R, 1.5–1.8 times fewer arteries narrowed than in the sham–operated (SO) rats. By day 21 after I/R, the constriction reaction was completely restored, except for arteries with a diameter more 40 μm. In the cell–therapy group, the constrictor response to GB was completely recovered to the level of SO animals in arteries with a diameter less than 40 μm by 14 day after I/R exposure; in arteries with a diameter of more than 40 μm, the constriction reaction did not recover until 21 days. The number of dilations per ACh/GB compared to a clear ACh in SO rats was reduced in 1.6–1.8 times on 14 day after I/R and in 1.6–6.6 after 21 days. In I/R animals on 14 day, the number of dilatations per ACh/GB compared to clear ACh was significantly increased in arteries with a diameter of more than 20 μm by 1.5–1.7 times, and after 21 days in arteries with a diameter of more than 40 μm by 1.2 times. After the introduction of hMSC, GB blocked ACh–mediated dilation in arteries less than 40 μm in diameter both on days 14 and 21 after I/R. In arteries with a diameter of more than 40 μm the functional activity of KATP-channels did not recover until 21 days. Conclusion. I/R of the rat cerebral cortex reduces the contribution of KATP-channels to maintaining the basal tone of the pial arteries and almost completely excludes these channels from the formation of ACh–mediated dilation during 21 days of the postischemic period. Practically did not participate in the dilatory response. Intravenous transplantation of hMSC, performed 7 days after I/R, results in restoration of participation of SMC KATP-channels in maintaining the basal tone and ACh–mediated dilatation of pial arteries with a diameter less than 40 μm already 14 days after I/R.

This study aimed to assess the efficacy of intravenous transplantation of human mesenchymal stem cells (hMSCs) to Wistar rats, performed on day 7 after cerebral ischemia/reperfusion (I/R), for the functional recovery of KATP channels in cerebral arteries. Using a device for intravital visualization of pial vessels, we studied arterial responses to the KATP channel blocker glibenclamide (GB), the activator of the same channels pinacidil (PI), acetylcholine alone (ACh), and ACh against the GB background (ACh/GB) 14 and 21 days after I/R (12-min 2-vessel occlusion/hypotension) and intravenous hMSC transplantation performed 7 days after I/R exposure. On day 14 after I/R, the number of arteries constricted in response to GB decreased by 1.5–1.8 times vs. sham-operated (SO) rats. By day 21, the constrictor response completely recovered, except for the arteries with a diameter >40 µm. In the cell–therapy rat group, the constrictor response to GB completely recovered to the level of SO animals in arteries with a diameter < 40 µm as soon as by day 14 after I/R, whereas in arteries with a diameter > 40 µm, the constrictor response did not recover until day 21. The number of ACh/GB- vs. ACh-mediated dilatations in SO rats decreased by 1.6–1.8 times on day 14 and by 1.6–6.6 times on day 21 after surgery. In I/R rats, the number of ACh/GB- vs. ACh-mediated dilatations significantly increased by 1.5–1.7 times in arteries with a diameter > 20 µm on day 14, and by 1.2 times in arteries with a diameter > 40 µm on day 21. After hMSC transplantation, GB blocked ACh-mediated dilation of arteries with a diameter <40 µm both on days 14 and 21 after I/R. In arteries with a diameter > 40 µm, the functional activity of KATP channels did not recover until day 21. It was concluded that I/R of the rat cerebral cortex reduces the contribution of KATP channels in vascular smooth muscle cells to the maintenance of basal tone in pial arteries and almost completely excludes these channels from the formation of ACh-mediated vasodilation throughout 21 days of the postischemic period. Intravenous transplantation of hMSCs, performed on day 7 after I/R, restores the involvement of KATP channels in both maintaining basal tone and ACh-mediated dilation of pial arteries with a diameter < 40 µm already on day 14 after I/R.

Cell therapy with mesenchymal stem cells (MSCs) may be a promising technique for cerebral blood flow restoration after transient ischemia. Before a practical application of the cell material, 7-9 days are required for its cultivation. We studied the efficacy of human MSC (hMSC) transplantation performed 7 days after cerebral ischemia/reperfusion (I/R) to help recover cerebral circulation. The intravital micrograph technique was used to comparatively evaluate the vasculature density in the pia mater and the reactivity of the pial arteries in response to acetylcholine (ACh) in rats after I/R (clamping of both carotid arteries and a simultaneous decrease in and strict maintenance of the mean BP at 45 ± 2 mm Hg for 12 min) and with/without hMSC transplantation. Perfusion (P) in the sensorimotor cortex was assessed using laser dopplerography. After 14 and 21 days, the vasculature density in I/R-affected rats was 1.2- to 1.4-fold and 1.2- to 1.3-fold lower, respectively, than that in the controls. The number of ACh-dilated arteries decreased 1.6- to 1.9-fold and 1.2- to 1.7-fold 14 and 21 days after I/R, respectively. After 21 days, the P level decreased 1.6-fold, on average. Administration of hMSCs on day 7 after I/R resulted in complete recovery of the vasculature density by day 14. ACh-mediated dilatation fully recovered only in arteries of less than 40 μm in diameter within 21 days. After 21 days, the P level was 1.2-fold lower than that in the controls but significantly higher than that in rats after I/R without hMSCs. Delayed administration of MSCs after a transient cerebral ischemic attack affords the time for the procedures required to prepare cell material for transplantation and provides a good therapeutic response in the pial microvasculature.

Arterial hypocapnia (AH), induced by voluntary or forced hyperventilation of the lungs, is accompanied by a decrease in cerebral blood flow (due to an increase in the arteriole tone) and an increase in the affinity of hemoglobin for oxygen. As a result, an oxygen supply to cortical tissue decreases and zones with a critically low oxygen tension (pO2) are formed in brain tissue. The distribution of pO2 in cerebral cortex during AH has not been studied enough. The aim of the work was to evaluate the effectiveness of oxygen supply to brain tissue at the level of arterial and venous microvessels at AH. To do this, the following tasks were set: (1) to study the distribution of the pO2 on the arterial and venous microvessels of the rat cerebral cortex; (2) to analyze tissue pO2 profiles near the walls of these microvessels. On anesthetized Wistar rats under conditions of forced hyperventilation (PaCO2 = 17.1 ± 0.7 mm Hg), the distribution of oxygen tension on the wall of pial and radial arterioles with a lumen diameter of 7–70 µm and on the wall of pial and ascending venules with a lumen diameter of 7–300 µm was studied. In tissue, near the wall of cortical arterioles and venules with a lumen diameter of 10–20 µm, tissue pO2 profiles were measured. Measurements of pO2 during spontaneous breathing of the animal with air served as a control. All pO2 measurements were made using platinum polarographic microelectrodes with a tip diameter of 3–5 µm. Visualization of the electrode tip and microvessels was carried out using a LUMAM-K1 microscope with epiobjectives of the contact type. This work presents for the first-time direct measurements of pO2 on the walls of arterioles and venules of the rat cerebral cortex and in tissues at different distances from the walls of these microvessels at AH. It has been shown that AH results in significant decrease in the oxygen supply to cerebral cortex, that is manifested by a significant drop of the pO2’s on venous microvessels and in tissue in the immediate vicinity of the studied microvessels. It has been shown, that the role of arterioles as a direct source of oxygen to brain tissue, is significantly reduced during arterial hypocapnia. Forced hyperventilation results in significant deterioration of oxygen supply to cerebral cortex, despite elevated pO2 values in the systemic arterial blood and in blood of systemic cerebral veins (sagittal sinus).

Reactions of pial arteries to exogenous hydrogen sulfide exposure and assessment of the contribution of K ATP and BK Ca channels to H 2 S-mediated dilation was studied in rats of different ages. Intravital microphotography in Sprague-Dawley rats aged 4 and 18 months was used to study the reactions of pial arteries of various diameters to the exposure of exogenous hydrogen sulfide donor solution—sodium hydrosulfide (NaHS, 30 µM), as well as their change with the preliminary use of potassium channel blockers: K ATP (glibenclamide, 10 µM) and BK Ca (tetraethyl ammonium, 2 mM). It was found that inhibition of H 2 S-mediated dilation of pial arteries and increase in constrictor responses to exogenous hydrogen sulfide exposure are taking place in rats with age. Age-related changes in H 2 S-induced dilatory response of the pial arteries in rats depend on the size of the vessels. With age, there is a decrease in the number of dilations of pial arteries with a diameter of more than 20 µm. At the same time, aging does not affect the dilatation of smaller arteries. These disorders are probably associated with changes in the processes caused by the activation of potassium channels. It was found that aging is accompanied by the increasing of K ATP -channels contribution to the implementation of H 2 S-mediated dilation in pial arteries with diameters less than 40 µm. BK Ca -channels contribution to the dilatation decreases with age. In 18-months-old rats, these channels barely participate in H 2 S-mediated dilation in arteries with diameters more than 20 µm.

The aim of this work was to study the effect of intravenous transplantation of human mesenchymal stem cells (hMSCs) on the functional state of KATP channels of smooth-muscle cells of cerebral arteries at different times of the postischemic period. Using a device for intravital visualization of pial vessels, the reaction of arteries to the KATP-channel blocker glibenclamide (GC), the activator of the same channels of pinacidil (PI), acetylcholine (ACh), and ACh against a background of GC action (ACh/GC) 7, 14, and 21 days after cerebral ischemia/reperfusion (I/R) and intravenous hMSC transplantation. On exposure to GC 7 days after I/R, two to five times fewer arteries narrowed than in the SO group and 1.5 times fewer expanded after PI. The introduction of hMSCs on the day of I/R of the brain after 7 days had no effect on the functioning of KATP channels: the constrictor reaction to GC and the dilator reaction to PI in this group were the same as in animals that underwent I/R. Fourteen days after I/R, the number of narrowed pial arteries on GС was 1.5–2 times less than in SO rats; the number of arteries that responded with dilatation to PI was 2–2.5 times less. In the cell-therapy group, for 14 days after I/R, the number of pial arteries that narrowed under the influence of GС and expanded under that of PI almost completely corresponded to those in SO rats. On day 21 after I/R, complete recovery of pial-artery responses to GC to the level in LO rats was observed. In the cell-therapy group, the reactivity of the pial arteries fully corresponded to the indicators in the SO group of animals. The functional state of KATP channels after I/R of the brain was assessed by comparing the dilator reactions of the pial arteries when exposed to pure ACh and ACh against a background of KATP channels being blocked with glibenclamide (ACh/GC). In SO animals, GC blocked the dilator reaction to ACh. The application of ACh against the background of GC increased the number of dilatations 7–14 days after I/R. After 21 days, the number of dilated vessels on exposure to ACh and ACh/GC was the same. In animals with transplanted hMSCs, excluding the first 7 days, GC blocked the dilator reaction of the pial arteries to ACh in the same way as in the SO group. It can be concluded that I/R of the rat cerebral cortex reduces the contribution of KATP channels to maintaining the basal tone of the pial arterial vessels. Changes persist for 14 days after ischemic exposure. At the same time, in the period from 7 to 21 days after I/R, the role of KATP channels in the dilatation of pial arteries on ACh decreased and by day 21 channels practically did not participate in the dilator response. Intravenous transplantation of hMSCs on the day of brain I/R results in earlier (as early as after 14 days) restoration of participation of SMC KATP channels in maintaining the basal tone and ACh-mediated dilatation of pial arteries.

The dynamics of changes in the vascular network density inthe sensorimotor cortex pial membrane, acetylcholine (ACh)-mediateddilation of the pial arteries, tissue perfusion and oxygen saturationwas studied in Sprague-Dawley rats after the formation of metabolicand hormonal disorders similar to metabolic syndrome (MS) and type2 diabetes mellitus (DM2). The rats were kept on a high-fat dietfor 2 months, and a part of them was then administered with low-dose streptozotocin(35 mg/kg). After that, all animals were fed a high-fat diet foranother one month. The number of vessels across a certain surfacearea of the sensorimotor cortex and the responses of pial arteriesto ACh (10–7 M) were assessed via intravitalmicroscopy. Tissue perfusion and oxygen saturation (SO2)levels were measured in the same animals using a multifunctionallaser diagnostic complex LAKK-M. It was found that a 3-month high-fatdiet led to the development of MS, i.e. elevated blood glucose levels,insulin resistance, and significant visceral fat gain. In the experimentalrats, the vascular network density in the pial membrane decreasedby 1.3–1.4 times vs. the control group, the number of pial arteriesdilated in response to ACh decreased by 1.2–1.6 times, the levelof tissue perfusion did not change significantly, but the SO2 leveldecreased by an average of 9%. In DM2 rats, there was no furtherrarefaction in the vascular network, but ACh-mediated dilation decreasedby 1.6–2.3 times vs. the control group. Tissue perfusion level decreasedby 22% and that of SO2 by 6%. Changes incerebral circulation begin with the development of MS. DM2 progressionentails endothelial dysfunction of the cerebral arteries: the lesserthe vascular diameter, the weaker the ACh-induced vascular dilation.The desolation of the vascular bed and impaired cerebrovascularreactivity negatively affect oxygen supply of brain tissue.

Changes in the contribution of intermediate conductance Ca2+-activatedpotassium channels (IKCa) to basal tone maintenanceand acetylcholine (ACh)-mediated dilation of pial arteries after globalcerebral ischemia (“2VO + hypo” model) were studied in 18-month-oldSprague–Dawley rats. Sham-operated rats served as a control. Vascularexamination was performed 7, 14 and 21 days after ischemia/reperfusion(I/R) using intravital microphotography. Changes in the contributionof IKCa channels to basal tone were assessedby the number of pial arteries constricted in response to the IKCa channelblocker clotrimazole (10–7 M, 5 min).Changes in the contribution of IKCa channelsto vascular dilation was evaluated by comparing the number and degreeof pial artery dilatations in response to ACh (10–7 M,8 min) before and after clotrimazole application. It was found thatI/R leads to a decrease in the number of vascular dilatations inresponse to ACh, which persists over the first 14 days after ischemicexposure. During this post-ischemic period, the contribution ofIKCa channels to pial artery tone and ACh-mediateddilatory response is also reduced. This phenomenon is already observed7 days following I/R, while after 14 days, IKCa channelsare practically no longer involved in the dilatory response of thepial arteries to ACh. By day 21 after I/R, all the above processesrecover.

BACKGROUND. Chronic kidney disease (CKD) is accompanied by the development of endothelial dysfunction, leading to a decrease in arterial reactivity to vasoactive agents. Uremia causes a change in the dilatation of arteries in various vascular regions, incl. and arteries of the pial membrane of the brain. The action of hydrogen sulfide (H2S), which can induce relaxation of smooth muscle cells of blood vessels, is currently considered a possible route of vasoprotection in various diseases, particularly, in CKD. THE AIM. To evaluate the role of calcium-activated potassium channels of large (BKCa) and intermediate (IKCa) conductance in H2S-induced dilatation of pial arteries in nephrectomized (NE) rats. MATERIAL AND METHODS. In Wistar rats nephrectomy (NE) was performed by resection of 5/6 of the renal tissue mass. Sham-operated (LO) animals served as control. The reaction of the pial arteries of the sensomotor cortex of NE and control SO rats to the application of H2S under physiological conditions and against the background of the use of BKCa channel blockers – tetraethylammonium (TEA) and IKCa – channels – TRAM-34. RESULTS. 4 months after NE, the application of H2S led to the dilatation of a smaller number of pial arteries (1.4 – 1.7 times) compared with SO rats. The preliminary exposure to TEA led to a decrease in the number of pial arteries responding by dilatation to the action of H2S in NE and SO rats. Against the background of the action of TRAM-34, the number of dilated arteries decreased under the action of H2S in SO rats, while in NE rats it practically did not change. CONCLUSION. Under physiological conditions, dilatation of the pial arteries in rats under the action of H2S is realized (at least in part) through the activation of the BKCa and IKCa channels of the membrane of endothelial and smooth muscle cells. Uremia, caused by nephrectomy, leads to impairment of the mechanism of dilatation of pial arteries, mediated by activation of calcium-activated potassium channels intermediate conductance apparently due to dysfunction of endothelial cells.

This study aims at examining how intravenous transplantation of human mesenchymal stem cells (MSCs) performed on the day of ischemia/reperfusion affects the vascular density and the reactivity of the pial arteries and tissue perfusion in the cerebral cortex 7, 14, and 21 days after ischemic exposure. The density of the entire microvascular network and arterial vessels in the pial membrane of the sensorimotor cortex of rats undergoing cerebral ischemia/reperfusion (I/P) and MSC intravenous transplantation were assessed with equipment for microcirculation monitoring. The same setup was used to study the reactivity of the pial arteries exposed to acetylcholine (ACh). In parallel, the perfusion index (PI) was measured in the sensorimotor cortex using a LAKK-M laser Doppler system. The density of the entire microvascular network and arterial vessels decreased more than in the case of sham-operated (SO) rats in the first 7 days after I/R: by 1.6 and 1.4 times on average, respectively. After 14 days, these indicators were 1.4 and 1.2 times; after 21 days, 1.2 and 1.3 times. In animals that underwent I/R, the reactivity of the pial arteries to ACh significantly declined. Seven days after I/R, the number of dilating arteries decreased by 1.4–1.7 times; after 14 days, by 1.6–1.9 times; and, after 21 days, by 1.2–1.7 times. After 21 days, the PI level decreased statistically significantly (on average, by 1.6 times). Intravenous administration of MSCs preserved the density of the microvascular network of the pial membrane in rats at the level of control animals at all periods after I/R. The PI 21 days after I/R was 1.2 times lower than in the SO group, but statistically higher than in rats with ischemic brain injury without MSC administration. It is concluded that intravenous transplantation of MSCs made it possible to prevent degradation of the microvascular bed in the cerebral cortex of rats after I/R and to preserve the reactivity of the pial arteries at the level of control animals. The reactivity in the cell therapy group also did not differ from the control values. The PI 21 days after I/R was 1.2 times lower than in the SO group, but statistically higher than in rats with ischemic brain injury without MSC administration. It is concluded that intravenous transplantation of MSCs made it possible to prevent degradation of the microvascular system in the cerebral cortex of rats after I/R and to preserve the reactivity of the pial arteries at the level of control animals.

Changes in acetylcholine (ACh)-mediated dilation of the pial arteries in the sensorimotor cortex were studied in Sprague–Dawley rats after the formation of metabolic and hormonal disorders similar to those in type 2 diabetes mellitus (DM2). For this purpose, the rats were kept on a high-fat diet (HFD) for 2 months, and then some of them were injected with a low dose of streptozotocin (STZ, 35 mg/kg). Next, all animals were again receiving high-fat foods for another one month (a total of a 3-month HFD). The responses of pial arteries to the effects of acetylcholie (ACh, 10 –7 M) alone or against the background of L-NAME, a non-selective nitric oxide synthase (NOS) blocker, or aminoguanidine (AG), a selective inducible nitric oxide synthase (iNOS) blocker, were assessed using intravital microscopy imaging technique. It was found that a 3-month HFD led to the development of endothelial dysfunction in the pial arteries of the sensorimotor cortex: the number of vessels dilated to the effect of ACh in the HFD group was 1.2–1.6 times smaller compared to the control group. ACh-mediated vascular dilation was endothelial NOS (eNOS)-depended only in the arteries with a caliber < 40 µm. In HFD rats, iNOS was not detected in the cerebral arteries. Animals with an STZ-induced DM2 model also developed endothelial dysfunction in the cerebral arteries: the number of vessels dilated to the effect of ACh in the DM2 group was 1.6–2.3 times smaller compared to the control group. In DM2 rats, the eNOS-associated signaling cascade did not control arterial reactivity, and vascular tone was mainly sustained due to iNOS-mediated reactions. In DM2 rats, the major abnormalities in the vascular dilatory response included the least number of vessels dilated in response to ACh alone with a significant decrease in the degree of dilation (by 1.5–1.6 times vs control), persistent ACh-mediated vascular dilation despite the presence of L-NAME, and the largest number of vascular constrictions in response to AG (60–70% of all the vessels examined). All these disorders were revealed in the pial arteries with a caliber < 40 µm, i.e. exactly in the vasculature segment that is maximally involved in blood–tissue gas exchange.

The changes in the contribution of ATP-sensitive potassiumchannels (KATP) to basal vascular tone maintenanceand acetylcholine (ACh)-mediated dilation of pial arteries afterglobal cerebral ischemia (2VO + hypo model) caused by a single cerebralischemia–reperfusion were studied in Wistar rats. Ischemia was modeledby bilateral carotid artery clamping for 12 min paralleled by maintainingthe mean arterial pressure at 45 ± 2 mm Hg. Sham-operated rats servedas a control. Vascular examination was performed on days 7, 14 and21 after ischemia. Changes in the contribution of KATP channelsto the basal vascular tone were assessed using intravital microphotographyby the number of vessels constricted in response to the effect ofa KATP channel blocker glibenclamide (10µM). Changes in the contribution of KATP channelsto vascular dilation were assessed by comparing the number and degreeof arterial dilation in response to ACh (10–7 M, 5min) before and after glibenclamide application. It was found thatischemia reduces the role of KATP channelsin basal vascular tone maintenance in pial arteries during 14 daysafter ischemic exposure. At the same time, the role of KATP channelsin the implementation of ACh-mediated dilatory responses of pialarteries also decreases. By postischemic day 21, KATP channelsare virtually no longer involved in the dilatory response to ACh.

The aim of this work is to study the deterioration of the contractile function of smooth muscle cells in pial arteries after subtotal nephrectomy, as well as the possibility of restoring this function by transplantation of human mesenchymal stem cells. A self-designed visualizing device for studying microcirculation (160× magnification) was used to study the reactivity of sensorimotor cortex pial vessels to hydrogen sulfide (H2S), L-NAME nonselective nitric oxide synthase inhibitor, and the combined application of H2S and L-NAME in sham-operated rats, nephrectomized rats, and nephrectomized animals that received human mesenchymal stem cells (hMSCs) intravenously. In parallel, the myogenic tone of cerebral vessels was assessed with a LAKK-M laser doppler. The results showed that, 4 months after nephrectomy in rats, the reactivity of pial arteries to H2S and L-NAME seriously deteriorated (the number of dilated arteries decreased by 1.2–1.7 times, and the extent of constriction was 6–17% smaller). The myogenic tone of cerebral vessels after nephrectomy was 1.5 times higher than in control rats. Intravenous hMSC transplantation allowed the myogenic tone and the reactivity of smooth muscle cells (SMCs) to be maintained at the level of control animals.

The changes in the contribution of ATP-sensitive potassium channels (KATP) in basal tone and acetylcholine (ACh) mediated dilation of pial arterial vessels after global cerebral ischemia (2VO + hypo model) were studied in Wistar rats. Vascular examination was performed 7, 14 and 21 days after ischemia. False- operated rats served as a control. The change in the contribution of KATP channels in basal tone was assessed using intravital microphotography. The number of vessels that constricted in response to the effect of the KATP channel blocker (glibenclamide, 10 μM) was assessed. The change in the contribution of channels in vascular dilatation was assessed by comparing the number and degree of arterial dilatation in response to ACh (10-7 M, 5 min) before and after the use of a KATP channel blocker. It was found that ischemia decreases the role of ATP-sensitive potassium channels in basal tone of the pial arterial vessels for 14 days after ischemic exposure. At the same time, the contribution of KATP - channels in the ACh mediated dilator reactions of pial vessels decreases. And by 21 days after ischemia, KATP channels do not participate in the dilator response to ACh.

— The aim of the investigation was to examine the effect of intravenous transplantation of human stem cells (hMSCs) on the main parameters of microcirculation (density of the microvascular network, reactivity of arterial vessels, tissue perfusion (TP) and oxygen saturation (SaO2)) in the cerebral cortex of rats after nephrectomy. Using an apparatus for studying microcirculation (magnification 40×), the density of the entire microvascular network and the density of arterial vessels in the pial membrane of the sensorimotor cortex of the brain of nephrectomized rats after intravenous transplantation of hMSCs were studied with equipment for the study of microcirculation. Equipment with greater magnification (160×) was utilized to investigate the reactivity of the pial arteries after exposure to acetylcholine (ACh). In parallel, the TP and SaO2 parameters in the sensorimotor cortex were measured with a LAKK-M laser doppler. The results showed that, 4 months after nephrectomy in rats (removal of five-sixths of the whole renal tissue), the density of the entire microvascular network and the density of arterial vessels decreased by an average of 1.3 and 1.5 times, respectively. The reactivity of the pial arteries after ACh exposure significantly reduced: the number of dilated arteries decreased by 2.1–4.4 times. TP (by 20%) and SaO 2 (from 94.8 ± 0.7 to 91.2 ± 1.8%) significantly decreased. Intravenous administration of MSCs restored the density of the pial membrane microvascular network (at the level of control animals) in rats after nephrectomy. All other parameters of microcirculation (reactivity, TP, and SO2) in the cell therapy group also did not differ from the control values. It was concluded that the use of hMSCs prevented degradation of the microvascular bed in the cerebral cortex of rats after nephrectomy and preserved the main parameters of microcirculation at the level of control animals.