Vasoconstrictor effect of acetylcholine in veins of the liver.

Intraportal acetylcholine administered to narcotized rats produced atropine-resistant constriction of hepatic veins, which was considerably prevented by phentolamine. Sodium nitroprusside produced a vasodilator effect. Similar results were obtained on isolated venous strip from the portal vein: acetylcholine-induced contraction was reduced by 25-50% in the presence of nicotinic receptor antagonist tubocurarine and cholinergic agonist nicotine and by 10% in the presence of tetrodotoxin. Probably, acetylcholine stimulates synthesis and release of a vasoconstrictor transmitter via nicotinic receptors of endothelial cells and/or portal vascular wall nerve terminals.

Insulin resistance of glucose response produced by hepatic denervations.

This study investigated the glucose response to insulin infused after hepatic denervation. Hepatic denervations were performed on 13 anesthetized cats at different levels: (i) surgical hepatic anterior plexus denervation, (ii) chemical total hepatic denervation by painting phenol on the tissues around the portal vein, bile duct, common hepatic artery, and hepatic ligaments, and (iii) bilateral vagotomy. Sham denervations were performed on 9 animals. Before denervation and after each performance of denervations, insulin (100 mU/kg, i.v.) was infused. Plasma glucose concentrations were analyzed at 15, 30, 45, and 60 min after insulin infusion. Hepatic anterior plexus denervation produced a significant reduction in insulin effectiveness. Phenol denervation and bilateral vagotomy failed to further significantly alter the level of insulin resistance developed by hepatic anterior plexus denervation. These observations demonstrate that the effect of insulin on glucose regulation is markedly reduced in the absence of hepatic anterior plexus innervation, suggesting that hepatic nerve function is necessary for the normal glucose response to insulin. Furthermore, the hepatic nerves of relevance appear to reach the liver primarily, if not exclusively, by the anterior hepatic plexus.

[Types of circulation in people with varying physical training]. / Tipy krovoobrashcheniia u liudei s razlichnoi fizicheskoi podgotovkoi.

In 125 young healthy males the cardiac output was estimated by means of tetrapolar rheoplethysmography. The marked differences were found in indices of central hemodynamics and specific peripheral resistance between the groups of sportsmen and non-sportsmen in spite of almost equal systemic arterial pressure in both groups. These differences are greatly due to the types of hemodynamics and in lesser degree--to the level of physical training and trend of sporting training.

Central nervous control of hepatic circulation.

This study was undertaken to assess the role of the hypothalamus and medulla oblongata in regulation of liver circulation in anesthetized dogs. Blood pressure, flow in hepatic artery and portal vein, and shifts of blood volume in the liver were recorded. Stimulation of the anterior hypothalamus produced changes in arterial pressure which were followed by passive changes in hepatic arterial blood flow; changes in hepatic artery resistance were rather small. Stimulation of the medial and posterior hypothalamus increased hepatic arterial resistance by 65-170%. Liver portal blood flow during stimulation of most of the hypothalamic sites decreased, hepatic portal pressure rose and vascular portal venous resistance increased 2.5-3 times. Three areas only (sympatho-inhibitory area, paraventricular and lateral hypothalamic nuclei) when stimulated produced dilatation of hepatic portal and splanchnic vascular beds, thus increasing portal blood flow. All cases of stimulation led to the decrease of blood volume in the liver by 10-36%. Stimulation of medullary structures (n. tractus solitarii, reticular nn.) caused similar changes in hepatic circulation, however the amplitude of reaction was 1.5-6 times smaller than upon hypothalamic stimulation. Central impulses to the hepatic vessels are transmitted by sympathetic adrenergic nerve fibers through vascular alpha-adrenoreceptors. It is concluded that the hypothalamic level of the central nervous system, unlike the bulbar one, exerts considerable, differentiated, well coordinated and to some extent specific influences on hepatic circulation.

[The effect of catecholamines on blood circulation in the liver]. / Vliianie katekholaminov na krovoobrashchenie v pecheni.

In acute experiments on dogs under nembutal anaesthesia the pressure and blood flow in the vessels supplying the liver have been recorded simultaneously with registration of the hepatic blood content changes. Catecholamines injected into liver vessels have been found to change significantly the liver circulation: adrenaline and noradrenaline evoke the constriction of intrahepatic vessels and decrease the blood content in the liver, realising through the alpha-adrenoreceptors activation, isadrin causes a weak vasodilatation by the activation of beta-adrenoreceptors. A selective inactivation of isadrin in the liver is shown. The density of alpha-adrenoreceptors distribution in the intrahepatic vessels is large enough and apparently some times exceeds the density of beta-adrenoreceptors. In 1/3 of dogs the beta-adrenoreceptors in the liver vascular bed are absent at all or present in arterial bed only.

[Neurogenic control of oxidative metabolism in the liver]. / Neirogennyi kontrol' okislitel'nogo metabolizma v pecheni.

In acute experiments on dogs, stimulation of the hypothalamic ventromedial nucleus induced changes of hepatic circulation and increased the rate of O2 consumption by the liver. In stimulation of supraoptic and lateral hypothalamic nuclei the hepatic O2 consumption changed insignificantly. The hypothalamic effects on the liver tissue respiration was blocked by obsidan (propranolol) but not by atropine. A correlation exists between shifts of the O2 consumption rate and those of temperature in the liver. The data suggest that hypothalamus can modify the liver oxidative metabolism through the sympathetic nervous system and beta-adrenergic receptors of the hepatocytes and redistribute the energy of this metabolism between processes of thermogenesis and endothermic reactions in the liver.

[Role of the hypothalamus in regulating liver circulation]. / Uchastie gipotalamusa v reguliatsii pechenochnogo krovoobrashcheniia.

In acute experiments on nembutal anesthetized dogs stimulation of anterior hypothalamus elicited changes in the hepatic artery blood flow, which followed those of arterial pressure; the vascular resistance remaining unchanged. The stimulation of medial and posterior hypothalamus led to decrease in flow and increase in the resistance of the hepatic artery. In most cases of hypothalamic stimulation the portal blood flow diminished, portal pressure and vascular resistance increased. The opposite reactions were observed during stimulation of sympathoinhibitory area, paraventricular and lateral hypothalamic nuclei. The conclusion is made that the hypothalamus participates in integrative and differential control of the hepatic circulation.

[Blood flow and oxygen tension and consumption in skeletal muscles after hypothalamic stimulation]. / Krovotok, napriazhenie i potreblenie kisloroda v skeletnoi muskulature pri razdrazhenii gipotalamusa.

In acute experiments on dogs under nembutal anesthesia, stimulation of different parts of the hypothalamus increased the muscle blood flow and O2 consumption and decreased vascular resistance. PO2 in m. gastrocnemius altered in both directions as a function of blood flow and O2 consumption changes. There was a good correlation between the initial level of PO2 and its shifts caused by hypothalamic stimulation. In most cases flow reactions were blocked with atropine. The stimulation of the hypothalamus seems to evoke cholinergic vasodilatation in skeletal muscles. The data suggest that initial level of muscle PO2 determines the redistribution of the increased blood flow between nutritional and non-nutritional vessels within the skeletal muscles and thus affects transcapillary exchange and O2 consumption during cholinergic vasodilatation.

[Differentiated interaction of hypothalamic and bulbar mechanisms in regulating blood flow in skeletal muscles]. / Differentsirovannoe vzaimodeistvie gipotalamicheskikh i bul'barnykh mekhanizmov v reguliatsii krovotoka v skeletnykh myshtsakh.

Acute experiments on dogs anesthetized with chloralose and numbutal were made to examine the changes in the blood flow in the muscles of hind limbs in response to stimulation of different parts of the hypothalamus before and after elimination of the effects of the main reflexogenic zones. Vasodilatation in leg muscles evoked by stimulation of the anterior hypothalamus (supraoptic dorso- and ventro-medial nuclei) increased after elimination of baroceptor effects. Qualitatively, the same response evoked by stimulation of the mamillary nuclei diminished. A conclusion has been made about differential interaction of the hypothalamic and bulbar mechanisms in muscle circulation control. It is assumed that vasodilatation of the skeletal muscles evoked by stimulation of the posterior hypothalamus might be determined by reflex inhibition of the vascular tone.

[Effect of several catecholamines on pulmonary circulation]. / Vliianie nekotorykh katekholaminov na legochnoe krovoobrashchenie.

In anesthetized dogs, i. v. injections of 0.1-1.0 mcg/kg adrenaline, noradrenaline, and isadrine evoked a raise of blood pressure in the right ventricle of the hear by 13-200%. The greatest pressor effects were obtained with isadrine, the smallest those--with noradrenaline. In experiments with closed chest animals with perfusion of lungs lobe by venous blood under constant pressure and recording of blood flow with photoelectric drop recorder, injections into perfusate of 0.02-32.0 mcg adrenaline and noradrenaline diminished blood flow and increased vascular resistance. In 1/3 of cases isadrine evoked the same reaction, in other cases it increased blood flow in perfused lobe and decreased resistance. The isadrine effect was blocked by beta--blocking agent inderal, whereas those of adrenaline and noradrenaline--by alpha-blocking drug phentolamine. Adrenaline and noradrenaline to constrict the pulmonary vessels by activating the vascular alpha-adrenoreceptors. Isadrine can dilate and constrict the lung vessels. In intact circulation isadrine seems to cause vasoconstriction and elevate blood pressure in lesser circulation.

[Vasomotor reactions of the pulmonary circulation upon hypothalamic stimulation]. / Sosudodvigatel'nye reaktsii v malom kruge pri razdrazhenii gipotalamusa

The blood flow in the lung lobe perfused under constant pressure was recorded with photoelectric drop recorder in acute closed-chest experiments in anesthetized dogs. Stimulation of supraoptic and lateral mamillary nuclei in most cases decreased flow rate and increased vascular resistance in perfused pulmonary lobe, while stimulation of sympatho-inhibitory area exerted opposite effect. Bilateral vagotomy and administration of atropin and inderal did not block the lesser circulation responses to the hypothalamic stimulation. However, phentolamine and bilateral ablation of stellate and upper thoracic ganglia eliminated chnages of blood flow and vascular resistance in the perfused lobe. The data obtained suggest that stimulation of some hypothalamic areas evoke obvious vasomotor responses in the lesser circulation and that these responses occur mainly through alpha-adrenergic sympathetic innervation of pulmonary vessels.

[Seasonal changes in cutaneous blood vessel tone in the frog Rana esculenta]. / Sezonnye izmeneniia tonusa kozhnykh sosudov liagushki Rana esculenta

Experiments have been carried out on frogs immobilized by diplacine. The diameter of arteries and veins in the web was measured before and after sectioning the sciatic nerve. Denervation of the hindlimb resulted in dilatation of web vessels, which was different at various seasons. Changes in the arterial tone were found to be polyphasic. The highest tone was observed in March, April and September, the lowest one-in May, August, October and January. Changes in the venous tone are less pronounced and follow biphasic pattern, the tone being increased in spring and summer and decreased in autumn and winter. Stimulation of the peripheral end of the sectioned nerve leads to the constriction of web vessels, its amplitude being dependent on the level of vascular tone at the given period of year. It is suggested that seasonal changes in the tone of cutaneous arteries are partially based on changes in the reactivity of the blood vessels.