[Interrelation between cardiac pump function disturbances and cardiac contractility after beta-adrenergic hyperstimulation of the heart in rats].

The complex of structural and functional changes of myocardium was investigated in experiments with rats with chronic beta-adrenergic activation for 1 month. We observed substantial attenuation of myocardial pump function, particularly reduction of stroke volume by 38.50% (P < 0.01), cardiac output by 42.38% (P < 0.01), and ejection fraction by 35.61% (P < 0.01). Furthermore, 2-fold increase of end-diastolic left ventricular pressure (P < 0.01) and rise of active relaxation constant Tau by 12.91% (P < 0.05) were observed. This indicates on an impaired diastolic function of the heart that is associated with accumulation of connective tissue elements in myocardium and increase of its end-diastolic stiffness that finally leads to cardiac pump function disturbances. Surprisingly, myocardial contractility was considerably augmented not only after the treatment with beta-adrenergic agonist but also on the 26th day after drug cessation. This phenomenon is associated with elevation of dP/dt(max) by 49.9% (P < 0.01), 2.5-fold increase of end-systolic elastance (P < 0.01) as well as maximal myocardial elastance by 42.53% (P < 0.05). It can be explained by compensatory influence of increased contractility that nevertheless failed to maintain adequate cardiac pump function and furthermore it may result in depletion of cardiac energy resource.

[The role of endogenous bioregulators in formation of cardiogenic reflex effects on circulation].

The possible role of endogenous endothelium-derived bioactive substances in organization of cardiogenic depressor reflexes under cardiac receptor stimulation (by veratrine and bradykinin) was investigated in acute experiments on anesthetized rats. The results have shown that endothelium-derived bioactive substances take part in forming of the cardiogenic depressor reflex humoral components of nervous response or nervous modulators. These data contribute to understanding of the role of endogenous endothelium-derived bioactive substances (prostacyclin) and different NOS isoforms in mechanisms of depressor reflex development and species differences in their involvement in reflex vasomotor reactions.

[Role of nitric oxide in the mechanisms of formation of reflex vasomotor responses].

This review focuses on modem data concerning the role of nitric oxide (NO) in the mechanisms of vasomotor regulation. On the background of the literature data and own experimental results, we have discussed some questions of NO integration into transmission of impulses in central and autonomic nervous system under condition of realization of cardiogenic and sinocarotid pressor and depressor reflexes, reflectory vasomotor responses formation under acute myocardial ischemia. According to literature and own functional and morphological data we suggest species differences in NO participations in mechanisms of reflex self--regulation of circulation.

[Central neuronal pathways in the Bezold-Jarisch reflex in rats].

The distribution of the Fos-immunoreactive (Fos-ir) and NADPH-diaphorase-positive/NOS-containing neurons in the medulla and thoracic spinal cord in rats was studied after the veratrine injection into v. jugularis ext. followed by reproduction of the Bezold-Jarisch reflex. Fos-ir neurons were found in the nucleus tractus solitarius (Sol), coudoventrolateral (CVL) and rostroventrolateral (RVL) areas, intermediate reticular nucleus (IRt), and lateral paragiganrocellular nucleus (LPGi) of the medulla. The intensity of c-fos expression was as follows: Sol > CVL > RVL > LPGi. The intensity of NADPH-diaphorase reactivity was manifested in the following sequence: Sol > IRt > LPGi > RVL. In comparison to sham-operated animals, application of veratrine is associated with a statistically significant increase (P < 0.01) of the mean number of Fos-ir neurons in the Sol and CVL, but not in the RVL. Double-labelling (Fos + NA DPH) was found in a small number (about 2%) of neurones in the Sol, IRt and LPGi. In the thoracic spinal cord Fos-ir neurons were predominantly detected in the superficial layers of the dorsal horn, area around the central canal and the intermediate lateral or medial nuclei (IMl and IMM), where NOS-containing neurons in the thoracic spinal cord were accumulated. Received data show that signals arising from the veratrine-activated cardiopulmonary afferents activate neurons of the Sol and CVL that together with the RVL are incorporated into neuronal circuits for generation of the Bezold-Jarisch reflex. In the medulla NOS-containing neurons activated by input from cardiopulmonary receptors can contribute to the enhancement of cardioprotective depressor reflexes in the rats.

[Characteristics of distribution of nitric oxide synthase containing neurons in the medullary cardiovascular centers of dogs and rats]. / Osoblyvosti rozpodilu neironiv, shcho mistiat' syntazu oksydu azotu v meduliarnykh sertsevo-sudynnykh tsentrakh sobak i shchuriv.

The aim of the study was to characterize species-related differences in the distribution of nitric oxide synthase (NOS)-containing neurons in the medullary structures of dogs and rats involved in the regulation of the sympathetic or parasympathetic drives. Two main results have been obtained, namely: (i) the average number of NOS-containing neurons in the dorsomedial and ventrolateral medulla per section in dog was larger than that in rat, while the density of the positive cells in the both regions in dog was less than that in rat. (ii) Within the dorsal motor nucleus of vagus a lot of NOS-containing cells (preganglionic vagal neurons) were observed only in dog. Differences in the distribution of NO-generating neurons in the medullary cardiovascular centers, and heterogeneity in the basal level of NO release may contribute to the peculiarities of the hemodynamic responses induced by NOS inhibitors in these species.

[Role of biologically active substances in the formation of cardiogenic reflex effects on circulation]. / Rol' biolohichno aktyvnykh rechovyn u formuvanni kardiohennykh reflektornykh vplyviv na krovoobih.

Analysis of the literary and own authors data about the participation some endogenous bioregulators (prostacyclin, bradykinin, nitric oxide) in the cardiogenic depressor reflexes formation is represented in this review. Possibility of chemosensitivity of the vagal afferent fibers for this substances and its role in the formation of cardiogenic effects on circulation is discussed.

[The role of endothelium-dependent factors in realizing cardiogenic reflexes under normal and pathological conditions]. / Doslidzhennia roli endoteliizalezhnykh faktoriv u realizatsiï kardiohennykh refleksiv za normal'nykh i patolohichnykh umov.

We have investigated the role of NO-dependent mechanisms in the realization of cardiogenic reflexes (pressor and depressor) during the action of veratrin and serotonin on cardiac receptors, adrenergic changes of the myocardial contractile activity or the short-term period of myocardial ischemia on anaesthetized dogs cats and rats. NO take place in the development of cardiogenic depressor reflexes and decreases pressor reflexes from the cardiac receptors in dogs. Specific characteristics of these influences were asserted: the depressor reflexes decrease after systemic inhibition of NOS by L-NNA in dog but they are increased or are not altered in rats. The depressor reaction in rats diminished after inhibition of nNOS performing by 7-nitroindazole. We affirm that NO-dependent influences have a compensatory effect in the course of acute alterations of the coronary blood flow and our statement concerning the advantageous role of NO-dependent mechanisms in the realization of self-regulatory reactions of circulation that connected with vagus nerve.

[Cardiac reflexes under conditions of heart injury]. / Kardiogenni refleksi za umov poshkodzhennia sertsia.

Analysis of the previous experimental literary data and own authors data about the pattern of cardiogenic reflectory effects during rise and development of the local injury is represented in this review. The role of double afferent innervation of the heart is discussed and author suggests its mayor functional role under some kind of heart diseases.

[The interrelation of neural and humoral cardiogenic influences and their action on the blood circulation]. / Vzaiemozv'iazok nervovykh i humoral'nykh kardiohennykh vplyviv i ïkh dia na krovobih.

The role of some endogenous bioregulators in formation of cardiogenic reflectory effects on circulation were investigated in acute experiments on anesthetized animals with using various methods (direct recording of impulse activity from cardiac afferent nerves, humoral isolation of the heart). Interrelations between development of cardiogenic depressor reactions and nitric oxide production was established. Systemic inhibition of NOS led to decrease in dilatation of coronary and peripheral vessels. At the other hand dramatic suppression of cardiogenic depressor reflexes followed by inhibition of prostacyclin production. The data support the essential role of endogenous bioactive substances in formation of cardiogenic reflex effects on circulation in physiological and pathological states. We also suggest that a mayor metabolite of arachidonic acid--prostacyclin--is modulator and one of humoral components of the vagus-mediated cardiogenic depressor reflex in physiological conditions.

[The effect of ionizing radiation on the nervous mechanisms regulating cardiac activity]. / Vplyv ionizuiuchoï radiatsiï na nervovi mekhanizmy rehuliatsiï diial'nist' sertsia.

Functional state of cardiac nervous links and pattern of cardiogenic reflectory responses to radiation (4 Gy) were studied in acute experiments on anesthetized rats at various periods after single radiation. The control level of nervous activity significantly varies in different terms after radiation. Intensification of parasympathetic effects and domination of depressor reactions are typical of the initial period (the 1st day). A decrease in the sympathetic tone and weakening of adrenergic influences are observed in all terms after radiation (from the 1st till the 14th day). Interrelationships between sympathetic and parasympathetic links of heart regulation as well as cardiogenic reflectory responses are not restored to the control level in remote terms after radiation (the 14th-20th days). So, single radiation of animals in a dose of 4 Gy has induced a disorder in the nervous heart regulation, which may be a cause of different pathological states.

[The mechanisms of the formation of cardiogenic afferent effects after the development of local immune damage to the heart]. / Deiaki mekhanizmy formuvannia kardiohennykh aferentnykh vplyviv pislia rozvytku lokal'noho imunnoho poshkodzhennia sertsia.

Sensitivity of cardiac receptors to several substances after local immune heart damage and the nature of cardiogenic influences on the circulation were studied in acute experiments o anesthetized dogs. The depressor reflexes from the heart were shown to disappear during 30 min. after immune heart damage, and vagal afferent impulse activity decreased. After immune heart damage, cardiac sympathetic afferent fibres were more sensitive to endogenous biological substances than to vagal ones. The sympathetic cardiac afferent system is found to be more sensitive to chemical agents, which is a decisive factor in formation of cardiogenic influences on the circulation during pathological processes in the heart.

[Cardiogenic influences on the blood circulation]. / Kardiogennye vliianiia na krovoobrashchenie.

The nature of cardiogenic influences on the circulation and the sensitivity of cardiac receptors to several substances after local immune damage of the heart, were studied: 30 min. after immune damage of the heart the depressor reflexes from the heart disappeared, and afferent impulse vagal activity was decreased. After immune damage of the heart, cardiac sympathetic afferent fibres are more sensitive to endogenous biologically active substances that vagal ones. The sympathetic cardiac afferent system seems to be more sensitive to chemical agent, being a decisive factor in the form of cardiogenic influences on the circulation during pathological processes in the heart.

[The heart as an endocrine organ]. / Serdtse kak éndokrinnyi organ.

Modern data on atrial natriuretic factor (ANF) are presented. Synthesis of this factor, its storage and release from cardiac atria are described. The role of ANF in the body fluid volume regulation and blood pressure homeostasis is discussed. ANF is regarded as a circulating hormone.

[The nature of cardiogenic sympatho-sympathetic reflexes in focal injuries of the heart]. / O prirode kardiogennykh simpatosimpaticheskikh refleksov pri ochagovykh povrezhceniiakh serdtsa.

The nature and dynamics of cardiogenic sympatho-sympathetic reflexes in response to intracoronary administration of veratrin, bradykinin, and to local immune heart injury were studied in anesthetized dogs. The sympatho-sympathetic reflex was shown to occur both in vagotomized and intact animals, though in the latter case the reflex was transformed due to descending influences from the bulbar center. The reflex was the least in case of veratrin administration and it was most obvious in bradykinin application or upon focal immune heart injury which indicates a greater sensitivity of sympathetic receptors to chemical agents.

[Mechanisms of the development of cardiogenic vagosympathetic reflexes]. / O mekhanizmakh razvitiia kardiogennykh vagosimpaticheskikh refleksov.

Mechanisms of development of cardiogenic vagosympathetic depressor reflexes during adrenergic heart stimulation and local immune and ischemic damages of the left ventricle were studied in anesthetized dogs and cats by recording afferent and efferent impulsation from cardiac nerves as well as cardiodynamic indices. Impulse activity in cardiac nerves showed reciprocal changes: an increase in frequency of afferent impulsation in vagal nerves and inhibition of efferent impulsation in sympathetic nerves. The data obtained suggest that stimulation of heart mechanoreceptors due to the increase of myocardial contractility and asynergy of the left ventricle, is a triggering mechanism for reflex inhibition of sympathetic impulsation and depressor reflex.