Myocardial serotonin during ischemia under conditions of ischemic preconditioning.

We studied the dynamics of interstitial serotonin during local myocardial ischemia under conditions of ischemic preconditioning in Wistar rats. Ischemic preconditioning increased serotonin content in the dialysate (p=0.003). During 30-min ischemia, ischemic preconditioning delayed serotonin increase just before the 20th min of ischemia. Ischemic preconditioning promoted short-term increase in the serotonin level in the myocardial interstitium but followed by prolonged ischemia, it delayed the accumulation of serotonin in the myocardial interstitium.

[Myocardial serotonin metabolism after local ischemia and ischemic precondition].

To determine the effect of ischemic preconditioning upon myocardial serotonin and 5-hydroxyindolacetic acid (5-HIAA) dynamic in myocardial ischemia and reperfusion. 28 male Wistar rats anesthetized with urethane were randomly divided into 2 groups. In the control group (n = 13) rats were subjected to 30 min coronary occlusion and subsequent 120 min reperfusion. In the ex- perimental group (n = 15) ischemic preconditioning (3 x 3 min ischemia + 3 x 3 min reperfusion) before prolonged ischemia was used. Myocardial interstitial serotonin and 5-HIAA were measured using a microdialysis technique. Myocardial serotonin and 5-HIAA significantly increased af- ter ischemic preconditioning (p = 0.00298; p = 0.00187). In prolonged ischemia interstitial serotonin level was lower in the experimental group vs. control up to 20 min of ischemia (p < 0.05). We conclude that ischemic preconditioning increases interstitial myocardial serotonin, but inhibit serotonin increase in subsequent prolonged myocardial ischemia. After 20 minutes of reperfusion the lack of correlation between serotonin and 5-HIAA levels appeared which may be the evidence of serotonin uptake activation.

[The role of asymmetric dimethylarginine in the regulation of nitric oxide level in rats with acute renal injury].

Nitric oxide (NO) is synthesized from arginine (ARG) by NO synthase (NOS). Asymmetric dimethylarginine (ADMA), a competitive inhibitor of NOS, participates in the endogenous regulation of NO synthesis. The main amount of ADMA is enzymatically degraded by dimethylarginine dimethylaminohydrolase (DDAH) widely expressed in renal tissue. The aim of our study was to compare the changes in DDAH activity and ARG synthesis in kidneys, ADMA and ARG concentration in plasma and their urinary excretion under physiological conditions and in acute renal injury (ARI) induced by glycerol in rats. Urinary nitrite/nitrate excretion (NOx) was estimated as an indicator of whole-body NO synthesis. DDAH activity was decreased, ADMA excretion was increased and plasma ADMA did not change in ARI. Plasma ARG concentration, renal ARG synthesis and urinary NOx excretion were decreased. In conclusion, the diminished enzymatic hydrolysis of the NOS inhibitor ADMA and the reduced synthesis of the NOS substrate ARG might affect NO production in ARI.

Inhibition of norepinephrine reuptake and size of myocardial infarction during focal ischemia and after preconditioning.

Experiments on rats showed that blockade of norepinephrine reuptake in the early reperfusion period after focal myocardial ischemia aggravates myocardial injury and abolishes the protective effect of ischemic preconditioning.

[Ischemic preconditioning and metabolism of myocardial adrenaline].

We implanted under urethane narcosis microdialysis probes into myocardium of Wistar rats. In experimental group we used ischemic preconditioning. After this left descending coronary artery was occluded for 60 minutes and then reperfused for 60 min. In control group prolonged occlusion was preceded by 30 min of rest. Significant elevation of noradrenaline concentration in myocardial interstitium was noted at 20th and 10th minutes of testing ischemia in experimental and control groups respectively. From 20th minute to the termination of occlusion noradrenaline concentration in myocardial in animals of control group was significantly higher than that in preconditioned animals. Concentration of dihydroxyphenylglycol in interstitium reflecting noradrenaline metabolism in axoplasm fell during ischemia and rose when reperfusion was started. Elevation of dihydroxyphenylglycol was statistically significant compared with both baseline level and control (p<0.005) practically at all stages of reperfusion. Thus ischemic preconditioning inhibits effectively noradrenaline accumulation in myocardial interstitium during prolonged ischemia. After ischemic preconditioning normal mechanism of noradrenaline reuptake functions longer however because of impaired storage in vesicles substantial part of noradrenaline remains in free state in axoplasm to be subjected to deamination with participation of monoamine oxidase.

[Uptake1 inibition in reperfusion: noradrenalin dynamic and myocardiola infraction size].

To determine the effect of uptake 1 inhibition in reperfusion after myocardial ischcmia upon noradrenalin dynamic and myocardial infarction size, 14 male Wistar rats anesthetized with urethane were randomly divided into 2 groups and subjected to 30 min coronary occlusion and subsequent 120 min reperfusion. In control group (n = 7) 1 ml of Ringer's solution was administered intravenously at the beginning of reperfusion. In experimental group (n = 7) instead of Ringer's solution 0.8 mg/kg of desipramine was used. Myocardial interstitial noradrenalin levels were measured using a microdialysis technique. Infarction size was determined by triphenyltetrazolium chloride staining and was related to the area at risk. Desipramine increased infraction size from 32.0 +/- 3.1 % (control group) to 46.1 +/- 3.4% (p = 0.06). Interstitial noradrenalin in experimental group did not decrease during 120 min reperfusion (p < 0.05 vs. control). The data obtained suggest that uptake 1 inhibition in reperfusion after myocardial ischemia increases myocardial infarction size through increased interstitial noradrenalin.

[Role of norepinephrine in myocardial ischemia and ischemic preconditioning].

A brief preceding ischemia-reperfusion can reduce infarct size; this is known as ischemic preconditioning. During myocardial ischemia, massive norepinephrine is released from the cardiac sympathetic nerve terminals, reflecting the sympathetic nerve injury, and producing myocardial damage. However norepinephrine participates in myocardial protection during ischemia since its depletion in nerve terminals prevents ischemic preconditioning, and exogenous norepinephrine mimics ischemic preconditioning. Multiple-valued role of norepinephrine in myocardial ischemia, and ischemic preconditioning is discussed in review.

[Noradrenaline dynamics in prolonged ischemia after ischemic preconditioning].

AIM OF THE STUDY: To determine the effects of two-staged ischemic preconditioning on myocardial noradrenaline in prolonged ischemia and reperfusion. METHODS: Thirty-two male Wistar rats anesthetised with urethane randomly divided into 2 groups: group 1 (ischemic preconditioning group, n = 16), and group 2 (control, n = 16). Myocardial interstitial noradrenaline levels were measured using a microdialysis technique. Ischemic preconditioning was elicited by two episodes: 5 min of ischemia and 10 min of reperfusion. The intermittent occlusions were followed by prolonged occlusion (60 min) and reperfusion (60 min). RESULTS: An increase in interstitial noradrenaline was observed in 10 min of prolonged ischemia in group 2, and in 20 min in group 1. After 20 min of myocardial ischemia there was a significant difference between groups (p < 0.05) in interstitial noradrenaline levels. In control group, it was 60% higher. In reperfusion, noradrenaline levels decreased markedly in group 1. CONCLUSION: We suggest that ischemic preconditioning by two episodes: 5-min ischemia and 10-min reperfusion prevents excessive noradrenaline interstitial accumulation, perhaps, through protection of physiological uptake I carrier.

[Asymmetric dimethylarginine: metabolism, arginine paradox, pathophysiology].

Pathophysiology of asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of NO synthase, has been a subject of intensive research activity during last years. The ways of ADMA synthesis and degradation were studied. It was suggested that ADMA plays a considerable role in the realization of so called "Arginine paradox". This paradox refers to the dependence of cellular NO production on exogenous L-arginine despite the saturation of NOS enzymes with intracellular L-arginine. Close association was described between increase in blood ADMA level and endothelial dysfunction accompanied by related pathologies like atherosclerosis, renal insufficiency, hypertension and some others. Some studies have represented ADMA as a strong independent risk factor for cardiovascular complications. Possible reasons are discussed of some experimental data ambiguity as well as the limits of confidence in clinical ADMA analysis.

[Norepinephrine of the rat myocardium during repeated ischemia].

Character of tissue changes as well as their reversibility could vary depending on the duration of myocardial ischemia. Long (over 30 min) ischemia leads to a massive release of myocardial interstitial norepinephrine. We tried to investigate changes in the myocardial sympathetic system produced by a relatively long episode of ischemia-repeperfusion. Myocardial norepinephrine has been collected by means of microdialysis probe during repeated occlusions of the left descending coronary artery. It was shown that long episode of occulusion-reperfusion resulted in suppression of massive norepinephrine release in response to second (test) occlusion. The features of norepinephrine release during successive occlusions make it possible to associate this process with the reversibility of the ischemic tissue damages.

Functional activity of the sympathoadrenal system in hypertensive NISAG rats.

NISAG rats with stress-induced arterial hypertension are characterized by hyperactivity of the sympathoadrenal system under rest conditions and during stress exposure.

Acquisition and extinction of a conditioned passive avoidance reflex in mice with genetic knockout of monoamine oxidase A.

We report here the results obtained from comparative analysis of learning and the dynamics of extinction of a conditioned passive avoidance response in mice with genetic knockout of monoamine oxidase A (MAO A) and the progenitor line C3H. Mice of both lines acquired the conditioned passive avoidance reaction efficiently. Mice with genetic knockout of MAO A were characterized by prolonged retention of reproduction of the memory trace, as compared with rapid extinction in C3H mice. Smaller numbers of transfers, and vertical rearings on days 7-13 and the numbers of glances into and rom the dark sector on days 11-13 of extinction in MAO A-knockout mice appear to reflect their more marked fear reactions when confronted with the "dangerous" sector, along with increased anxiety, these facilitating longer-lasting retention of the memory trace.

[Training and extinction of passive avoidance in mice lacking monoamine oxidase A].

The passive avoidance learning and memory trace retention in mice lacking monoamine oxidase A (MAO A) and control C3H strain were analyzed. It is shown that mice of both strains were well the passive avoidance learners. A delay of the memory trace extinction was found in lacking MAO A mice as compared with control C3H strain. Mice with a genetic MAO A knockout showed decreased amounts of transitions, rearings, looking to a dark compartment and appearing from it. These findings seem to reflect more expressed fear reaction to a dangerous compartment and increased anxiety promoting longer retention of memory trace on a high level of retrieval.

Hypothalamic monoamines in cold stress on the background of changes in the activity of the nitric oxide system.

The effects of the NO donor sodium nitroprusside and the NO synthase blocker L-omega-N-nitroarginine (LNA) on body temperature, hypothalamic monoamines, and plasma corticosterone in conditions of cooling were studied in Male Wistar rats. Reductions in body temperature on cooling, both after administration of sodium nitroprusside and LNA, were no different from those seen without treatment. The basal corticosterone level after treatment with sodium nitroprusside increased from 5.3 +/- 2.2 to 29.1 +/- 1.8 microg%. Cooling led to a multiple increase in corticosterone levels in all animals, both in control conditions and after treatment with sodium nitroprusside and LNA. Sodium nitroprusside significantly decreased the basal hypothalamic noradrenaline level, by 37%. Cooling of the animals in these conditions led to an additional drop in the noradrenaline level. Noradrenaline levels 48 h after cold stress applied to animals cooled after treatment with LNA or sodium nitroprusside were significantly higher than in those cooled without treatment. No changes in serotonin and 5-hydroxyindoleacetic acid levels were seen in these experiments. The basal dihydroxyphenylacetic acid and dopamine levels increased after treatment with sodium nitroprusside, by 379% and 239% respectively. No dopamine response to cold was observed, though the dihydroxyphenylacetic acid level in the control group and animals treated with LNA increased. Thus, cold stress did not reveal differently directed directions for the actions of the NO donor and the NO synthase blocker, as seen with other types of stress.

Effect of monoamine oxidase gene knockout on dopamine metabolism in mouse brain structures.

Experiments were performed on knockout Tg8 mice lacking monoamine oxidase A gene that plays a major role in dopamine catabolism. The study by the method of high-performance liquid chromatography revealed considerable regional differences in the contents of dopamine and its metabolite dihydroxyphenylacetic acid in brain structures of these animals. Tg8 mice differed from the parent C3H/HeJ strain by low level of dihydroxyphenylacetic acid in the striatum, midbrain, hypothalamus, and hippocampus and high concentration of dopamine in the striatum. No differences were revealed in the contents of dopamine and dihydroxyphenylacetic acid in the frontal cortex and amygdala. The 2.4-4.8-fold decrease in the content of dihydroxyphenylacetic acid in various brain structures was not accompanied by changes in dopamine concentration. These data reflect the effective compensation for deficiency of dopamine metabolism. Our results suggest that monoamine oxidases A and B and catechol-O-methyltransferase play different roles in dopamine metabolism in various brain structures.

[Hypothalamic monoamines in the cold stress during changes in activity of nitric oxide system]. / Monoaminy gipotalamusa pri kholodovom stresse na fone izmenenii aktivnosti sistemy oksida azota.

Effects of NO-synthase inhibitor N(omega)-nitro-L-arginine (LNA) and donor sodium nitroprusside (SNP) on alteration in body temperature, plasma corticosterone level and hypothalamic monoamines in response to cold exposure, were studied. Drop of the body temperature in cold exposure in rats treated with LNA or SNP was the same as in the control group. Administration of SNP (2 mg/kg i.p.) significantly increased the basal level of corticosterone (CS). Cold exposure elevated CS in all groups of rats. LNA did not markedly alter the hypothalamic noradrenaline (NA) while SNP significantly decreased the NA. Cold exposure resulted in additional decrease of the NA in SNP-treated rats. NA was found to significantly increase within 48 hrs following the cold exposure in the LNA as well as in the SNP groups. SNP significantly increased basal dopamine and DOPAC levels. Cold exposure did not affect hypothalamic dopamine. In the experiments, NO changes of serotonin and 5-hydroxyindoleacetic acid were observed. The findings suggest that antagonistic effects of the NO-synthase inhibitor and NO donor postulated in literature for various kinds of stress do not occur in experiments with cold stress.

[Effect of local and systemic desipramine administration on extracellular noradrenaline in the myocardium of rats]. / Vliianie lokal'nogo i sistemnogo vvedeniia dezipramina na uroven' vnekletochnogo noradrenalina v miokarde krys.

Evaluation of a local activity of the sympathetic system on the basis of norepinephrine (NE) level in the blood of myocardial vessels depends on at least three processes: NE release by sympathetic neurons, its reuptake and spillover of NE into the blood. The relations between these processes are different in various organs. Direct investigations of changes in the myocardial NE level under the effect of reuptake blockade by desmethylimipramine (DMI) were performed after appearance of the microdialysis technology. In this work the effects of local (through microdialysis membrane) and systemic administration of DMI on the NE release in a rat myocardium, were compared. Local DMI delivery increased myocardial NE level to 153 +/- 13% of the control level (0.17 +/- 0.026 ng/ml dialysate). NE concentration increased to 582 +/- 84% of control as a result of i.m. administration of 5 mg/kg DMI. No changes of the NE level in the venous blood were registered after systemic DMI. It is suggested that a relatively weak effect of local DMI is determined by saturation of DMI receptors adjacent to the probe and/or progressive diminution of the DMI effect with an increasing of the distance from the probe. Effect of systemic DMI administration depends on uniform blockade of all myocardial DMI receptors as well as the DMI influence on higher levels of the sympathetic system.

[Characteristics of responses of the sympatho-adrenal system to various types of cooling]. / Osobennosti reaktsii simpatoadrenalovoi sistemy krys pri raznykh tipakh okhlazhdeniia.

Fast cooling involving the dynamic activity of the skin cold receptors seems to establish a condition for changes in catecholamine concentration at a lesser decrease of body temperature as compared with slow cooling.

[An improved method for microdialysis study of noradrenaline level in rat myocardium]. / Usovershenstvovannaia metodika mikrodializnogo issledovaniia soderzhaniia noradrenalina v miokarde krysy.

A level of myocardial norepinephrine (NE) is considered as one of the meaningful parameters in the estimation of myocardium functioning. Long lasting changes of myocardial NE appear to be not only a sequence of pathologic processes in myocardium, but could also be a factor responsible for some diseases. An improved microdialysis sampling technique with HPLC-ED analysis was developed to measure in vivo NE content in a rat myocardial interstitium. Linear polyacrylonitryl 5 mm probes were flushed with methanol while being immersed in water. In vitro NE recovery with the flow rate of perfusate was found at the level 67.9 + 0.4%. Probes were implanted into the rat myocardium under the general anaesthesia. Myocardial dialysate was collected during 20 min into plastic vials, containing 10 microliters of 0.1 M perchloric acid. Low noise, high sensitivity dual electrochemical detection was used for the determination of NE amount in the samples. Overall sensitivity threshold was found about 0.3 pg of NE in 20 microliters. Steady state concentration of NE in myocardial dialysate was found 54 + 7 pg/ml. 20 min before cardiac arrest the concentration of NE in myocardial dialysate was found to be increased 4-5 times. 40 min after cardiac arrest further increase in NE content was registered up to 1-4 ng per ml of perfusate. It is suggested that the method will be useful for routine study of myocardial NE.