[Interaction of the inotropic effect of norepinephrine and acetylcholine on the guinea pig's myocardium]. / Vzaiemodiia inotropnogo vplyvu noradrenalinu ta atsetylkholinu na miokard morskoi svynky.

The experiments on guinea pig myocardium slices have been carried out to study the interaction of inotropic effects of different doses of norepinephrine (NE, from 10(-7) to 10(-5) mol/l) and acetylcholine (AC, from 10(-8) to 10(-6) mol/l). With an increase of NE concentration the negative influence of AC on the inotropic action is replaced by positive one. It is shown that there are optimal concentrations of NE and AC to exert a negative influence of AC on adrenergic inotropic effect (in these experiments--3 x 10(-7) mol/l for both influences). A decrease in frequency of contractions of AC on NE effect and positive influence of adrenergic myocardium stimulation on inotropic effect of AC, respectively. Such a type of relation of cardial effects of choline- and adrenergic influences is suggested to be designated by term "negatively accentuative antagonism" unlike the opposite type of choline-adrenergic interaction--"positive accentuative antagonism", under which AC increases inotropic effect of adrenergic myocardium stimulation, while adrenergic positive inotropic influences decrease AC effect.

[The topological characteristics of rat myocardial reactivity to noradrenaline, acetylcholine and a change in the electrostimulation frequency]. / Topolohichni osoblyvosti reaktyvnosti miokarda shchuriv na noradrenalin, atsetylkholin ta zminu chastoty elektrostimuliatsiï.

Dose-dependent effects of noradrenaline (10-7-10-6M), acetylcholine (10-8-3x10-6M) and stimulation rate (0.2-2.0 Hz) were obtained in experiments on myocardium preparations of the right and left atria and ventricles in rat. Three types of topological differences of the rat myocardium reactivity were observed: between the atria and ventricles (A/V), between the right and left atria and ventricles (R/L), between the right atrium (RA) and other cardiac chambers. A/V differences were most pronounced in the reactivity to acetylcholine (the atria were more reactive), the highest R/L differences were observed in the reactivity to noradrenaline (the myocardium of the right chambers was more reactive). RA reactivity greatly exceeded reactivity of other myocardial preparations to all three test influences. Topological peculiarities of chrono-inotropism permit supposing, that inotropic effects of rate changes in vivo are able to compensate, to some extent, the regional nonuniformity of cholin- and adrenergic regulatory inotropic effects.

[Age-related changes in inotropic effects of noradrenaline and acetylcholine on the myocardium of guinea pigs]. / Starechi zminy inotropnoï diï noradrenalinu ta atsetylkholinu na miokard mors'kykh svynok.

The inotropic effects of noradrenaline (10(-7)-10(-5) M) and acetylcholine (10(-8)-10(-6) M) were studied in experiments carried out on preparations of the right atria and on papillary muscles of the right ventricle in adult (4-5 months) and old (18-24 months) guinea pigs. An age-related decrease in inotropic noradrenaline effects and the displacement of dose-effect relationships to the right was revealed. Similar changes of the dose-related effects of acetylcholine superfused against the background of noradrenaline action were observed. The direct inotropic action of the acetylcholine did not change with ageing. A lack of the essential atrial-ventricular differences in age-related changes in myocardial reactivity is apparently very significant for support of effective functional coupling of cardiac chambers in ageing.

[Interatrial differences of myocardial reactivity and its changes in adaptation of rats to physical exercise]. / Mezhpredserdnye razlichiia reaktivnosti miokarda i ee izmenenii pri adaptatsii krys k fizicheskoi nagruzke.

The myocardial reactivity to main regulatory influences (changes of stimulation rate, superfusion of acetylcholine, adrenaline, noradrenaline) was to be higher in right than in left rat atrium. The training-induced increase of some interatrial differences in myocardial reactivity suggests their essential physiological significance.

[Interaction of inotropic effects on acetylcholine, adrenaline and increase of atrium stimulation frequency in rats adapted and non-adapted to physical exercise]. / Vzaimodeistvie inotropnykh vliianii atsetilkholina, adrenalina i uvelicheniia chastoty stimuliatsii predserdii u adaptirovannykh i neadaptirovannykh k fizicheskoi nagruzke krys.

It is shown in experiments carried out on the isolated strips of the left and right atria of the rat that adrenaline decreases the inotropic effect of acetylcholine while interatrial differences of chrono-inotropy are elevated by acetylcholine and adrenaline. Training of animals changes interaction of regulatory effects in such a way that an increase of the negative chrono-inotropy is compensated and efficiency of the cardiac muscle regulation grows.