[Possible mechanism of hyperemia in the skin caused by non-painful mechanical pressure].

It is believed that hyperemia in the skin, resulting from applied weak mechanical pressure delays the development of ischemia, and that it is a defensive neurovascular reaction against the local pressure, which can be considered as a critical point in terms of prevention of ischemia and, respectively, the risk for development of bedsores. Taking into account that nitric oxide can be released from autonomic nerves and make a significant contribution to the functioning of the mechanism of neurogenic vasodilation in different tissues, and the fact that the same role can also play the calcitonin gene-related peptide, the aim of this study was to clarify the role of each of these factors in the development of local hyperemia caused by non-painful, mechanical pressure on the skin. In experiments on white rats with a quantitative measurement of the intensity of skin blood flow, it was confirmed that in case of non-painful pressure acting on the skin, two-phase reaction of local blood flow appears - at first there is an increase in its level, and then an exponential decrease with stabilization at a level below the initial one. Analysis of received data allow to make conclusion that in relization of this phenomenon the role of trigger element belongs to nitric oxide, and the role of the executing unit - to calcitonin gene-related peptide. The effectiveness of this combined mechanism is limited by development of dominance of pressor-induced mechanical compression of cutaneous vessels over its vasodilator effect.

[Pharmakological characteristic of some amide local anesthetics, currently used in dental clinics].

Along with the brief history of amide local anesthetics development, their most important properties (from the viewpoint of use in clinical dental practice), are also reviewed. In particular, some properties of most commonly used local anesthetics, such as lidocaine, mepivacaine, prilocaine, bupivacaine and articaine are analysed. The most important data concerning pharmacological mechanisms of mentioned anesthetics' action, that cause certain features and peculiarities of their clinical application are given in condensed form. Besides, some precaution measures that must be taken into account in specific clinical cases together with the history and current status of each patient are mentioned as well.

[Possible role of nitric oxide in newborns weight gain disorder caused by prolonged dexamethasone therapy (experimental study)].

Experimental studies on rats revealed that the newborns growth retardation, caused by long-term treatment with Dexamethasone in the neonatal period, can be prevented by the simultaneous with dexamethasone administration of the nitric oxide donor--L-arginine. This indicates that the mentioned Dexamethasone-induced growth disorder is caused by inhibition of Nitric Oxide Synthases activity.

[Possible mechanism of behavioral disorders in rats under long term treatment with dexamethasone in neonatal period].

Despite the fact that the side effects of prolonged treatment with dexamethasone are well known, information about its effects on the central nervous system is very limited. Experimental study of long-term effects of dexamethasone administration in the neonatal period on behavioral activity of rats in the open field was conducted. Four groups of newborn males were selected from the offspring of pregnant rats. The first group was left intact, the animals of second group were injected saline solution, the third group - with the dexamethasone and the fourth group - along with dexamethasone received L-arginine. Tests in an open field for all groups of animals were carried out on the 45th (first test) and 60th (second test) days after birth. The results showed that the decrease in motor activity of animals and in the number of sectors crossed in the open field with a high statistical significance was observed only in the group of animals, which for four days in the neonatal period underwent dexamethasone treatment. At the same time, another group of animals, which was also injected dexamethasone in the same doses, but additionally was injected L-arginine, the behavior in the open field did not differ from the intact animals or animals which were injected (as a control) saline solution. It was concluded that it is the lack of nitric oxide in the early neonatal period, which occurs as a result of dexamethasone treatment that causes observed changes in animals' behavior.

[Iodine deficiency in the prenatal period may form learning ability deficiency in the postnatal period].

The present study analysis the changes in learning ability of the progeny of rats suffered from iodine deficiency. Reduction of serum thyroxin in the mothers' blood during three months before mating and whole period of gestation to an average level of 4,7+/-0,6 ng/ml, significantly worsened the learning ability in progeny, and the reduction to 1,1+/-0,4 ng/ml - completely deprived progeny's learning ability. Passage of the maze for these animals was purely probabilistic in nature without any signs of learning We can conclude that the diet with very low iodine content results in a low level of thyroxin in maternal serum and neurological deficiency in progeny manifested by learning disability during maze testing. Addition of the iodine to the diet prevents development of mentioned neurological deficiency.

[Main factors determining the functional state of pregnant rat's uterus].

In a review article the authors based on the analysis of the literature, conclude that the Calcitonin Gene-Related Peptide (CGRP) inhibits myometrial contractility at the background of the nonselective Nitric Oxide Synthase inhibitor (L-NAME) action. Along with this, there are evidences that in NOS-deficient rats the process of pregnancy proceeds normally. Thus, literature data indicate that CGRP, independently of Nitric Oxide is included in the myometrium relaxing system, which of course does not exclude its joint action with both Nitric Oxide and other relaxing factors. Moreover, according to our data L-Arginine, causes complete inhibition of spontaneous contractile activity of the rats' myometrial strips, but the administration of L-NAME, eliminates the inhibitory effect - contractile activity was restored.

[Analgetic property of nonspecific thalamic nuclei].

Neruronal activity evoked by pain impulsation in the specific thalamic nuclei and sensorimotor cortex has been recorded in cat. The following data were obtained. Evoked nociceptive neuronal activity was inhibited by stimulation of the nonspecific thalamic nuclei. An antinociceptive impact of the nonspecific thalamic nuclei on the specific thalamic units was fulfilled by both direct and thalamo-cortico-thalamic pathways. Stimulation of the antinociceptive regions of the nonspecific thalamic nuclei abolished evoked nociceptive activity of the cortical units, elicited by both peripheral noxious stimulus and stimulation of the ventro-postero-medial thalamic nuclei. This indicates that the nonspecific thalamic nuclei inhibit the cortical activity on the thalamic, as well as, on the cortical level.

[Effect of lidocaine and lidocaine with adrenaline on development of cerebral seizures].

Experiments were carried out on male albino rats of 200-250 g weight with bipolar electrodes implanted in neocortex, as well as in the right and the left dorsal hippocampus for the study of the effect of lidocaine and its combination with adrenaline on the electric activity of brain. On the fifth day from the implantation in the first group of animals 0,3 ml 2% lidocaine was injected intra-peritoneally and the electric activity from the above mentioned structures was registered. In the second group 0,3 ml 2% lidocaine with adrenaline was injected intra-peritoneally (1:100000). In 8-12 sec after injection in the first group of animals the encephalogram showed sharply defined clone type seizure activity, which soon obtained tonus character. Simultaneously clone-tonus type behavioural manifestation was revealed, which lasted for 20-25 minutes. In the second group of animals in 30-40 sec after injection the encephalogram revealed convulsion activity with high amplitude synchronous oscillations, which lasted for 20-25 minutes, although in this group, in distinct from the first group, no clone-tonus behavioural manifestation was detected.

[Local blood flow in the dorsal hippocampus and cerebellar cortex in progeny of iodine-deficient rats].

Experimental studies show depressive behavior in rats caused by hypothyroidism and antidepressant effect of thyroid hormones. The present study analyses changes in the hippocampal and cerebellar cortex local blood flow in the progeny of rats suffering from iodine deficiency before mating and during the whole period of gestation. The diet with very low iodine content results in a decrease of local blood flow in both brain structures, but the greatest changes were observed in hippocampus. Addition of the iodine to the diet eliminates the above blood flow changes.

[Assessment of the lower threshold in autoregulation of the blood supply of the optic nerve disk].

Existence of the autoregulation phenomenon in the blood supply system of the optic nerve has been established in the 1990; however, some of its quantitative and qualitative characteristics still require clarification. The goal of the present work was assessment of the lower margin in autoregulation of the blood supply of the optic nerve in the rabbit in conditions of attenuated level of perfusion pressure. Total of six adult rabbits weighing 2.5-3.0 kg, anesthetized with urethane (0.9-1.1 g/kg) were investigated in acute experiments. Intensity of the local blood flow in the optic nerve disk was evaluated quantitatively by means of the hydrogen clearance. The frontal chamber of an eye was punctured with syringe needle, which via silicon tube was attached to the reservoir filled with artificial aqueous humor. Adjustment of vertical position of the reservoir provided different levels of the intraocular pressure. Calculation of the perfusion pressure of the eye was made according to mean level of the systemic arterial pressure, intraocular pressure, and a constant, which depends on an animal species. The results obtained allow suggesting with a certain degree of precision that elevation of the intraocular pressure to about 40-50 mmHg does not alter the blood supply of the optic nerve disk. Its further increase however leads to almost linear dependence between elevation of the intraocular pressure and decrease of the blood supply of the optic nerve disk. Meanwhile, the systemic arterial pressure should be considered as well, because volume of the perfusion pressure in the eye is determined by difference between systemic arterial- and intraocular pressures.

[Open field testing of the progeny of rats with iodine deficiency].

Experimental studies show depressive behavior of rats caused by hypothyroidism and anti-depressive effect of thyroid hormones. The present study analysis changes in emotional state of the progeny of rats suffered from iodine deficiency of different severity before mating and during whole period of gestation. The basic diet with low content of iodine markedly decreased animal's motor activity and that was clearly demonstrated in open field testing. More pronounced changes in open field behavior was observed in group of animals with more restricted iodine diet (addition of KClO(4) to the basic diet) -- animals show significant decrease number crossed squares, number of entering into central squares and vertical standings, and increased frequency of gumming. Addition of the iodine to the diet prevents development of the mentioned changes.

[The effect of electrical stimulation of the cerebellar fastigial nuclei on local blood flow in the brain]. / Vliianie élektricheskoi stimuliatsii fastigial'nykh iader mozzhechka na mestnyi krovotok v golovnom mozge.

In acute experiments on unanesthetized cats, continuous recording revealed an increase (30%) as well as a decrease (70%) in local blood flow in the sensomotor cortex of the left hemisphere in response to electrical stimulation (30 Hz, 30 V) of the contralateral fastigial nuclei of cerebellum. The stimulation seems to lead to a primary vasoconstriction as well as vasodilatation of the blood vessels regulating the local cerebral blood flow.

[Electrical activity of the cerebellum during the sleep-wakefulness cycle]. / Elektricheskaia aktivnost' mozzhechka v tsikle bodrstvovanie-son.

Spontaneous electrical activity of the cerebellar cortex and fastigial nuclei was studied in unrestrained cats with implanted electrodes. Rhythmic (4-8/s) electrical activity was recorded in the fastigial nuclei of the cerebellum in paradoxical sleep as well as during some fragments of active wakefulness. A weak correlation between these processes was revealed by means of cross-correlation analysis of electrical activity in the fastigial nuclei and dorsal hippocampus. During wakefulness and in different phases of sleep some high-amplitude waves occur in the cortex of cerebellar vermis, their frequency sharply increasing with the onset of the paradoxical sleep. Functional significance of the changes in electrical activity of the cerebellum in sleep-wakefulness cycle and their possible mechanisms are discussed.

[Prolonged negative potentials of the surface of the sensomotor cortex of the cat and responses of neural and glial cells]. / Dlitel'nye otritsatel'nye potentsialy poverkhnosti sensomotornoi kory koshki i reaktsii nervnykh i glial'nykh kletok.

In acute experiments on immobilized cats, potentials evoked by stimulation of the ventrolateral and intralaminar thalamic nuclei, of the surface of the sensorimotor cortex and pyramidal pathways as well as the corresponding postsynaptic responses of pyramidal neurons, were studied. A negative shift of potential in response to tetanic stimulation of the cortical surface or thalamic nucleus occurred on the cortical surface. Concominantly, intracellular recording of the glial-cell activity was performed. Superficial application of strychnine induced the suppression of the slow-negative potential arising during direct cortical and primary responses and the corresponding slow potentials of IPSP. The effects of iontophoretic application of strychnine on IPSP of pyramidal neurons and cortical glial-cell response were also studied. Both ways of application appeared to block mainly the early component of IPSP during which the input resistance was significantly lesser than that of the late component, pointing to the difference in their genesis. The findings indicate that slow-negative potentials reflect hyperpolarization of pyramidal neurons, while the separate components of responses have common genesis.

[Analysis of prolonged evoked potentials of the cerebral cortex]. / Analiz dlitel'nykh vyzvannykh potentsialov kory bol'shikh polusharii.

Evoked responses of the motor cortex (dendritic and slow negative potentials) elicited by its direct electrical stimulation, primary, nonspecific and antidromic responses elicited by stimulation of ventrolateral and intralaminar thalamic nuclei and pyramidal pathways and the respective postsynaptic responses of neurons were studied in acute experiments on curarized cats. The potentials evoked during direct cortical stimulation, as well as during stimulation of specific and nonspecific thalamic nuclei and pyramidal pathways were recorded from one and the same point of the motor cortex, while the respective intracellular responses--from one and the same neuron. It is demonstrated that slow negative potentials evoked under these stimulation conditions and the corresponding IPSP follow an identical time-course. The results obtained indicate that the slow negative potential is the reflection of hyperpolarization of pyramidal neurons. The individual components of various evoked potentials recorded from the cortical surface are supposed to be of common genesis.

[Negative surface potential shift and neuronal and glial cell response to tetanic stimulation of the surface of the cortex]. / Otritsatel'nyi sdvig potentsiala poverkhnosti i reaktsii nervnykh i glial'nykh kletok pri tetanicheskom razdrazheii poverkhosti kory.

Intracellular neuronal and glial activity in response to tetanic stimulation of the cortical surface or thalamic nuclei and accompanying cortical surface negative potential shifts were recorded in lightly nembutalized curarized cats. Glial cells responded to such stimulation by slow depolarization which under certain conditions of stimulation was replaced by slow hyperpolarization. Neurons responded by hyperpolarization. No correlations between depolarization and hyperpolarization of glial cells as well as between neuronal hyperpolarization and negative surface potential shifts were shown at simultaneous recordings of such shifts and glial neuronal responses. It is suggested that the negative surface potential shift is of a complex origin and is produced by both glial and neuronal somatic and dendritic responses.