[Effect of chemical sympathectomy on the development of DOCA-salt hypertension in rats]. / Vliianie khimicheskoi simpatéktomii na razvitie DOKA-solevoi gipertensii u krys.

Structurally based resistance and vascular reactivity of the posterior body to noradrenaline were studied in normotensive rats and rats with DOCA-salt hypertension. The hypertension was induced in rats with intact sympathetic nervous system and in rats subjected to neonatal sympathectomy with guanethidine. During the prehypertensive stage, vascular sensitivity of the smooth muscles to noradrenaline was enhanced, with structural lesions being observed only in steady hypertension. Elevation of arterial pressure was accompanied by an increased vascular response to the stimulation of the sympathetic nerves. Sympathectomy prevented arterial pressure elevation and structural alterations in the vessels.

[Age-related changes in the sympathetic innervation of effector organs in the rat after partial sympathectomy with guanethidine]. / Vozrastnye izmeneniia simpaticheskoi innervatsii éffektornykh organov posle chastichnogo razrusheniia simpaticheskoi sistemy u krys s pomoshch'iu guanetidina.

Guanethidine (30 mg/kg daily for first 15 days of life) decreased by 85% the amount of cells in the rat upper cervical sympathetic ganglion for 4 months. In ageing, the volume of the ganglion's cells, the density of adrenergic fibers and the noradrenaline content in the heart, intestine and ductus deferens increased in the desympathized animals. The neural cells remaining after desympathization seem to develop a growth of axons and to restore to some extent the density of sympathetic innervation of the periphery. The firing rate of single preganglionic fibers of the cervical sympathetic nerve is increased in the desympathized animals. The increased firing rate seems to be the cause of changes in the surviving neurons.

Growth of sympathetic postganglionic axons after partial chemical destruction with guanethidine.

Partial sympathectomy of neonatal rats was produced by treatment with guanethidine. The number of neurons of the superior cervical ganglion decreased to 15% of control values and remained constant throughout the subsequent observation period of 4 months. The volume of the remaining neuronal perikarya increased faster than that of control animals during the observation period, and the density of adrenergic innervation of the iris and the noradrenaline content of the heart were found to partially recover after the initial decrease produced by the guanethidine treatment, reaching 33% and 30% of control values, respectively, after 4 months. The noradrenaline content of the duct of the vas deferens was greatly reduced by guanethidine treatment, but almost recovered after 4 months. The frequency of sympathetic preganglionic impulses was elevated throughout the 4 months observation period, and it is suggested that this increase is responsible for the compensatory changes in cell volume, terminal density and terminal noradrenaline content of the remaining neurons.

[Adaptation of the peripheral organs of rats to noradrenaline deficiency following chronic desympathization]. / Adaptatsiia perifericheskikh organov krys k nedostatku noradrenalina pri khronicheskoi desimpatizatsii.

In 3--week guanetidine--desympathized rats, the noradrenaline (NA) concentration in myocardium, small intestine and ductus deferens constituted 1, 6 and 3% of the control, resp., whereas release of the NA from the ductus deferens on transmural stimulation dropped to 3%. From 4 to 16--week age the NA content in myocardium and small intestine reached 30 and 23%, resp., and its release was equal to control. The diminishing of NA content was followed by augmented adrenaline--sensitivity and diminished cholinosensitivity of the organs under study. Significance of local adaptive mechanisms for normalizing of activity of the adrenergic nervous system under conditions of desympathization, is considered.

Arterial pressure, cardiac output and exercise hyperemia in chemically sympathectomized rats.

This study showed that arterial blood pressure of chemically sympathectomized rats (SR) was decreased, whereas heart rate was increased relative to controls. The cardiac output in SR was higher than that in intact animals (by 36% under urethane anaesthesia and by 80% without anaesthesia). The total peripheral resistance of SR was 1.7 times less than normal, although the magnitude of the structural component of resistance was increased. The half-time clearance of 133Xe from skeletal muscle during motor nerve stimulation was greater in SR than in intact rats by a factor of 2. It is concluded that the number of small resistance vessels in SR is low, while the lumen of individual vessels is greater than in controls, thus giving rise to an insufficient "vasodilator reserve".

[Circulatory features of "chemically" desympathized rats]. / Osobennosti krovoobrashcheniia u "khimicheski' desimpatizirovannykh krys.

Desympathized rats developed a lower arterial pressure, a higher heart rate and a greater one--minute blood volume heart output as compared to intact rats. The total peripheral resistance in the major circulation of desympathized rats is by 1.7 times lesser although their structural component of the resistance is higher. The latter finding seems to be due to a reduce density of vessels per unit of tissue volume. The time of half--washing of Xe33 out of intramuscular depot in working hyperemia during motor nerve stimulation is nearly twofold in desympathized rats. The humber of small resistance vessels seems to be lessened per unit of tissue volume in desympathized animals whereas the lumen of separate vessels in them is larger than in normal animals. This accounts for considerable reduction of the range of vasomotor vascular regulation in desympathized animals.

Effect of sympathectomy on platelet aggregation and blood coagulation in rats.

It is shown that the ability of blood platelets to aggregate in partially and completely sympathectomized rats is significantly lower than in intact animals. The blood clotting system of sympathectomized rats is hyperactive. The sympathectomy-provoked changes may be due to the increased content of adrenaline in the blood.

[Effect of desympathization on thrombocyte aggregation capacity and the blood clotting potential of rats]. / Vliianie desimpatizatsii na agregatsionnuiu sposobnost' trombotsitov i koaguliatsionnyi potentsial krovi u krys.

It was shown that platelet aggregation in partially (with stellate ganglia containing 25% neurons of normal amount) and completely (0,5% neurons) sympathectomized rats was significantly lower than in intact animals. Concurrently the blood coagulation system of sympathectomized rats was hyperactive. The reasons for sympathectomy-induced changes seems likely to be elevated adrenalin blood concentration in such rats.

[Tissue fibrinolytic activity of different sections of the heart in sympathectomized animals]. / Fibrinoliticheskaia aktivnost' tkanei razlichnykh otdelov serdtsa u desimpatizirovannykh zhivotnykh.

In the heart of intact rats aged 6 and 10 weeks the activity of nonenzymatic fibrinolysis was found to be maximum in the auricular tissue. In partly sympathectomized (destruction of 75% of neurons in the ganglia) 10-week-old rats fibrinolytic activity was sharply reduced in the auricular tissue, and in the atrial and ventricular myocardium. The content of the plasminogen activator in all parts of the heart decreased to zero value. In stress situations 50% of the rats die from thrombi in the atrial cavity. In partly sympathectomized 10-week-old rats (characterized by restoration of peripheral sympathetic innervation) the studied parameteres were normalized. The fibrinolytic potential of the heart tissue was markedly decreased in totally sympathectomized rats (destruction of more than 99.5% of the neurons); under the effect of stress 80% of these animals died.

[Noradrenaline concentration in peripheral organs and their adrenosensitivity following chemical desympathization]. / Soderzhanie noradrenalina v perifericheskikh organakh i ikh adrenochuvstvitel'nost' pri khimicheskoi desimpatizatsii.

The rats desympathised with guanetidine developed a 58% decrease of the noradrenaline content in the myocardium, 37% - in the deferent duct, and 82% - in the small intestine. No significant changes of the catecholamines content occurred either in adrenal glands or in the hypothalamus. Sensitivity of the deferent duct's adrenoreceptors increased by 9 times. Sensitivity of the small intestine to noradrenaline increased by 3.4 times whereas the sensitivity to the antagonistic transmitter acetylcholine decreased by 2.4 times. Local adaptation mechanisms maintaining functioning of the organism in chronic desympathisation, are regarded.

[Study of the destruction of the sympathetic ganglia by the administration of guanethidine to newborn rats and mice]. / Issledovanie destruktsii simpaticheskikh gangliev pri vvedenii guanetidina novorozhdennym krysam i mysham.

Following the injection of guanethidine (25 mg/kg) to rats from the first day of life during 2 weeks, over 70% of sympathic neurons in the stellate ganglion die. If the injections are carried out during 4 weeks, over 99% of neurons die. The injection of guanethidine to mice during 5 weeks did not result in the destruction of nerve elements in the ganglion, as compared with the control.