[Cardiomyocyte culture as a highly sensitive system for testing pharmacological activity of specific bradycardic agents].

Two antiarrhythmic agents were studied: verapamil and bradizole, a new bradycardic drug. It was found that both drugs exhibit a dose-dependent negative chronotropic effect on the culture of contractile cardiomyocytes of newborn rats. Bradizole showed more pronounced bradycardic properties than verapamil.

[The positive chronotropic effects of salsolinol on the isolated rat heart]. / Polozhitel'nye khronotropnye vliianiia sal'solinola na izolirovannom serdtse krysy.

Salsolinol (6,7-dioxy-1-methyl-1,2,3,4-tetrahydroisochinoline), a product of nonenzymatic condensation of dopamine and acetaldehyde, produced a dose-dependent positive chronotropic effect on the rat isolated perfused heart: EC = 5.6 X 10(-6) M. Inderal, a beta-adrenoreceptor antagonist (10(-5) g/ml), blocked and naloxone, an opioid receptor antagonist (3.1 X 10(-5) M), potentiated this effect. Apart from tachycardia, salsolinol induced arrhythmias which were inhibited by naloxone. Salsolinol seems to play an important role in regulating the heart performance.

[Increase in the efficiency of parallel fiber synapses on Purkinje cells of the frog after simultaneous activation of climbing and parallel fibers]. / Uvelichenie éffektivnosti sinapsov parallel'nykh volokon na kletkakh Purkin'e liagushki posle odnovremennoi aktivatsii liannykh i parallel'nykh volokon.

Ability of the Purkinje cells to long-term plasticity changes after joint stimulation of parallel and climbing fibres has been studied in the isolated cerebellum-medulla oblongata preparation of frog. 18 neurons have been chosen on the ground of the presence of clearly identifiable monosynaptic response to parallel fibre stimulation and stability of the background activity within two hours. These neurons belonged to three distinct categories: those having the clear climbing fibre response, those having the climbing fibre-like response and those without the climbing fibre response. The neurons of the first group showed a significant increase of the ability to respond to parallel fibre stimulation after joint stimulation of both types of fibres. The stimulating current strength which was necessary for the Purkinje cell firing index 1/2 was reduced after conditioning procedures in this neuron group to 0.7 of its original value. There were no substantial changes in parallel fibre stimulation efficiency in two other neuron groups.

[Effect of calcium antagonists on action potentials of muscle fibers in the warm-blooded]. / Vliianie "antagonistov kal'tsiia" na potentsial deistviia myshechnykh volokon teplokrovnykh.

The effect of the "calcium antagonist" D600 (5.10(-6)--1.10(-4) g/ml) on the amplitude, duration and rate of the rise (Vmax) on the action potential (AP) of mouse diaphragm muscle fibers were studied. To evoke and record the AP, a standard microelectrode technique was employed with two microelectrodes being inserted into the same fiber about 50 micrometer apart. The fibers were stimulated by a single pulse or by serial ones. D600 was shown to reduce the amplitude and Vmax of AP and to increase its duration both in innervated and denervated muscle fibers. The magnitude of the membrane potential and the input resistance were not affected by D600. After denervation the sensitivity of muscle fibers to D600 fell. In the course of stimulation applied by serial pulses (1--2 Hz) instead of single ones, the inhibitory effect of D600 drastically increased. It is suggested that D600 strongly modifies the activity of fast sodium channels, the manifestations of the effect being controlled by innervation.

[Analysis of the activity of fibers in an entire nerve trunk and a study of impulse frequency in sympathetic preganglionic fibers]. / Analiz aktivnosti volokon v obshchem nervnom stvole i issledovanie chastot impul'satsii v simpaticheskikh preganglionarnykh volokon.

The firing rate in type "B" preganglionic sympathetic fibers during strong pressor reactions varied in different fibers from 0 to 80/sec. With an increase of the pressor reaction, the maximum of the density of frequency distribution shifts from 30--40 to 50--60/sec, previously "silent" fibers becoming involved.

[Bioelectrical activity and automatic properties of different parts of a two-chambered heart]. / Issledovanie bioélektricheskoi aktivnosti i avtomaticheskikh svoistv razlichnykh otdelov dvukhkamernogo serdtsa

Two pacemakers localized in sinoatrial and atrioventricular valves were revealed in the tench heart. In their absence, the ventricular and sometimes the atrial myocardium are capable of initiating the automaticity. Pacemaker's cells of the sinoatrial valve are surrounded by specific area similar to sinoauricular ring in amphibia or sino-caval region in mammals. Characteristics of the action potential in different parts of the tench heart are presented.

[Transistorized electrometric intensifier for recording low-amplitude bioelectric activity]. / Tranzistornyi élektrometricheskii usilitel' dlia otvedeniia nizkoamplitudnoi bioélektricheskoi aktivnosti

An amplifer is described which is intended to register a low amplitude bioelectric activity at intra- and extracellular recordings using high ohm electrodes. The increase of real sensitivity (increase of the ratio signal/noise) is reached selectively for each case by a smooth change of the amplifier frequency band, as well as by applying field transistors with little noise at the output stage of the amplifier.