[Mechanism of "autoregulation" of the cerebral circulation: role of neurogenic and myogenic vascular reactions]. / O mekhanizme "autoreguliatsii" mozgovogo krovoobrashcheniia: rol' neirogennykh i miogennykh sosudistykh reaktsii.

The neurogenic and pure myogenic responses of the dog circulatory isolated internal carotid artery were studied under conditions of controlled intraluminal pressure changes. The artery was continuously perfused with the oxygenated bicarbonate Ringer-Krebs solution, and the vascular responses were estimated as changes in the perfusion fluid flow rate recorded with a drop-flowmeter. The quantitative analysis of the vascular responses showed that a comparatively constant perfusion fluid flow independent of the rate of perfusion pressure changes only occurred when the neurogenic control of the artery was preserved. The pure myogenic responses of the artery were only observed in 25% of tests, were four times weaker and present only within the narrow limits and at a specific rate of the intraluminal pressure changes.

The effect of ethyl apovincaminate on vasospasm of the circulatory isolated internal carotid artery in dogs.

The vasodilator effect of ethyl apovincaminate (Cavinton) was studied upon the circulatory isolated internal carotid arteries (in dogs), which had been proved to be a typical locus of vasospasm in the cerebral arterial system. The effects of ethyl apovincaminate were studied under conditions of experimental spasm produced in the artery. The drug caused a dilator effect which was considerably greater and longer-lasting than that of theophylline. The dilatory effect of ethyl apovincaminate was the greater the higher was the initial tone of the arterial smooth muscles. Neither accumulation of the drug nor habituation of the vascular wall was observed when ethyl apovincaminate was administered repeatedly. The effects of the drug considerably decreased when Ca++ was eliminated from the arterial wall. It regularly decreased the vasoconstrictor effects of serotonin and increased K+ in the perfusion fluid and boosted the vasodilatory effect of theophylline upon the artery. On the other hand, increase of cyclic AMP in the vascular wall potentiated the effect of ethyl apovincaminate, while PGE2 decreased the latter.

[Relationship between the tonus of the walls of the internal carotid artery and cyclic adenylmonophosphate]. / Zavisimost' tonusa stenok vnutrennei sonnoi arterii ot tsiklicheskogo adenilmonofosfata.

Experiments were carried out in dogs with the use of resistography of circulatory-isolated internal carotid artery. Both activation of adenyl cyclase by adenosine and inhibition of phosphodiesterase by theophylline in the vascular wall result in a significant decrease in the vasoconstrictor effect of prestaglandin E2. On the contrary, inhibition of adenyl cyclase by the beta-blocker propranolol or activation of phosphodiesterase by imidazol in the vascular wall causes potentiation of vasoconstriction brought about by prostaglandin E2. Thus the endogenous cyclic AMP either antagonizes the vasoconstrictor effect of prostaglandin E2, or the latter affects vascular smooth muscles by influencing the activity of enzymes that are responsible for the cyclic AMP level in the vascular wall.

[Effect of prostaglandins E1 and E2 on the internal carotid artery]. / Deistvie prostaglandinov E1 i E2 na vnutrenniuiu sonnuiu arteriiu.

Experiments were conducted on the dog internal carotid artery (with circulatory isolation); the following peculiarities of the effects of the prostaglandins (PG) under study were revealed: PG-E1 caused either a constrictory or a dilatory effect, and PG-E1--a constrictory effect only; in the former case the artery became accustomed with repetition of the action, and in the latter case it did not become accustomed. The duration of the PG-E2 effects, particularly of relaxation, was much greater than of the serotonin effects; residual contraction of the vascular smooth muscles was frequent; PG-E1 and PG-E2 intensified the effects of serotonin, and, partially, of noradrenaline.

[Pathological and compensatory processes in the cerebral circulation during blood transfusion shock]. / Processus pathologique et compensatoire dans la circulation cérébrale lors du choc d'hémotransfusion.

In experiments on dogs the intravenous injection of heterogenous blood resulted in a decrease of total arterial pressure, weakening of the brain blood flow, fall of Po2 and pH in the brain cortex. A simultaneous constriction if inner carotid arteries is depending on direct action on the vascular wall of heterogenous proteins and on a release in it of physiologically active substances, such as serotonin. Fine pial arteries were dilated by the compensatory mechanism that was not associated with a decrease of intravascular and with direct action of hypoxia or acid metabolites on vascular walls. It was proposed that the trigger mechanism of this vasodilatation is hypoxic changes of metabolism in the nervous tissue.

[Possible participation of prostaglandins A1 and B1 in the development of internal carotid artery spasm]. / O vozmozhnom uchastii prostaglandinov A1 i B1 v voznikovenii spazma vnutrennikh sonnykh arterii.

Experiments were carried out on dogs with the internal carotid artery circulatory isolated and continuously perfused in situ with oxygenated Ringer-Krebs bicarbonate solution. Prostaglandins A1 and B1 (PG-A1 and PG-B1) exerted a constrictory effect on the artery. The effect of both prostaglandins was significantly less, but more prolonged than that of the same doses of serotonin. A possible role of PG-A1 and PG-B1 in the development of vasospasm is testified to by the following experimental results: a) during repeated action of PG-A1 AND PG-B1 their effect did not change, and therefore it should not decrease under prolonged influence of these prostaglandins on the vascular wall;) b) the mentioned prostaglandins caused potentiation of the constrictory effect of both serotonin and norepinephrine.

[Characteristics of the functional behavior of different cerebral arteries and angiospasm location in them]. / Osobennosti funktsional'nogo povedeniia raznykh arterii golovnogo mozga i lokalizatsiia v nikh angiospazma

For the major arteries of the brain, when their tone is normal, the constrictory responses are much greater than the dilatory ones while the tendency to dilation of the pial arteries is considerably greater than their tendency to constriction; some luminal contraction and no dilation of the intracerebral arteries (in the depth of the cortex) appears even at an increased blood flow. The tendency to a spasm of the cerebral arteries is corroborated by the peculiarities of their functional behavior: the spasm-like constriction of the major arteries of the brain occurs much easier than that of the pial arteries; a spasm of the intracerebral arteries may develop, but only under some local effect.