Behavior Disorders Caused by Perinatal Hypoxia in Juvenile Rats and Their Correction with GABA Derivative

We studied the effects of acute normobaric hypoxia on postnatal day 2 (model of preterm pregnancy) on reflex activity and behavior of juvenile male Wistar rats and the possibility of correction of behavioral deficit by administration of GABA derivative Salifen after hypoxia. It is shown, that perinatal hypoxia impaired righting reflex and forelimb grip strength and increased motor activity in juvenile male rats. Administration of Salifen for 14 days in a dose of 15 mg/kg improved reflex activity and behavior of rats, which indicates the prospect of further study of the therapeutic efficacy of this drug on models of neonatal encephalopathy.

[LONG-TERM EFFECTS OF EXPOSURE TO PERINATAL HYPOXIA ON MICROVASCULAR ENDOTHELIUM OF NEOCORTEX IN RATS]

Morphological characteristics of the elements of vessel walls in the microvasculature of rat neocortex were studied after perinatal hypoxia and subsequent introduction of salifen, a derivative of GABA, at long-term postnatal periods. It is shown that salifen at a therapeutic dose has a protective effect on the endothelium of blood vessels in the microvasculature of neocortex. It is found that after exposure to hypoxia followed by application of salifen no endothelial hypertrophy, appearance of numerous processes of endotheliocytes in the vascular lumen, and narrowing of the capillary lumen occur. The formation of la- mina densa is almost identical to that in the control. Swelling of perivascular astrocytes and reactive chan- ges of pericytes are also absent. In all layers of the neocortex the density of vessel distribution in the mic- rovasculature as well as their cross-sectional area in adult animals of the control group and after exposure to hypoxia and salifen application were approximately identical. It is shown that changes and restructu- ring of the capillary bed after exposure to hypoxia and application of salifen take place at earlier terms of development whereas by the maturity period stabilization of the structural parameters of the microvas- culature occurs. The protective effect of salifen on the elements of capillary walls determines the clinical effectiveness of its use and serves as a basis for further research in this direction.

[REACTION OF STRUCTURAL ELEMENTS OF HEMATOENCEPHALIC BARRIER IN NEWBORN RATS TO NORMOBARIC HYPOXIA]

For the last time a particular interest of investigators has been attracted to the period of early newborn state when active process of adaptation of the organism to new life conditions occur defining its increased sensitivity to the effect of unfavorable environmental factors. An important place among these processes belongs to formation of homeostasis mechanisms and, primarily, the barrier mechanisms. The purpose of the present study was to investigate reactions of the hematoencephalic barrier (HEB) to action of perinatal normobaric hypoxia (a model of incomplete human pregnancy). Using light and electron microscopy, our investigation showed that after action of hypoxia all wall elements of neocortex capillaries revealed structural alterations which may cause impairment of microcirculation and increased permeability of HEB. It is established that differentiation of the basal membrane of a capillary wall takes place during the early perinatal period and the indicator of its differentiation is the formation of its plates - laminae rara et densa. After action of hypoxia, besides a delay of formation of the basal membrane, a vesicular type of its degeneration occurs. Key words: perinatal hypoxia, hematoencephalic barrier, capillary, endothelial cells, basal membrane.

[THE EFFECT OF PERINATAL HYPOXIA ON THE STRUCTURE OF BLOOD-BRAIN BARRIER IN RATS TREATED WITH SALIFEN]

The work was performed on Wistar rats, which were dividedinto 3 groups: 1st group--experimental rats subjected to hypoxia and treated with salifen (15 mg/kg for 14 days), 2nd group--control rats exposed to hypoxia only without treatment, and 3rdgroup--intact animals (8-10 animals in each group). Using themethods of light and electron microscopy, the effect of salifen onthe structural characteristics of the elements of the blood-brainbarrier (BBB) in the neocortex was studied in rats after exposureto hypoxia in the early postnatal period--on postnatal Day 2(model of human preterm pregnancy). The results showed thatsalifen had a positive effect on the state of the microvasculatureafter perinatal hypoxia, in particular, on the state of endothelialcells. Its active participation in the compensatory-adaptive reactions of the BBB in response to hypoxia exposure was detected,and the prospects of further studies of the protective properties ofsalifen are emphasized.

[Reactions of neural elements of neocortex on action of hypoxia at the early neonatal period in rats]

In this work we studied reactions of neural elements of various neocortex areas (sensomotor, visual, auditory) on action of acute normobaric hypoxia. The study is performed on the model of human premature pregnancy (action of normobaric hypoxia on rat pups at the 2nd postnatal day). There are revealed monotypical and monodirected structural reconstructions in all studied neocortex parts. The chosen parameters of hypoxic action initiate several direct reactions as early as at the next day: a decrease in sizes of cell bodies and in volume of the cytoplasm, as well as an enhancement, as compared with control, of the apoptotic cell death. By the end of the neonatal period (5 days), several ultrastructural alterations indicating deceleration of processes of differentiation of nerve cells are revealed: arrest of processes of complication of smooth and rough endoplasmic reticulum and of Golgi apparatus, a small number of single ribosomes and polysomes in the cytoplasm, a decrease of the number of growth cones of axons and dendrites in neuropil, delay and disturbance of myelination processes in nerve fibers. The detected morphofunctional reconstructions can serve the structural ground for development of neonatal encephalopathies.

[Reactions of the interneuronal synapses of rat brain to hypoxia during the early postnatal period]

The reactions of forming synapses in rat neocortex to the effect of hypoxia in the early postnatal period (day 2) were studied. Using immunocytochemistry for synaptophysin demonstratoion and electron microscopic methods, the sensorimotor cortex was studied in rats at days 3, 4 and 10 of postnatal development (6 to 10 animals of each age) in both experimental and control groups (intact animals). Immunocytochemical study of the control animals demonstrated significant differences in the quantitative distribution of synaptophysin-positive structures in the different layers of the neocortex in the early postnatal period of development (day 5). It is shown that after exposure to perinatal hypoxia, more than 2-fold decrease of the optical density of the immunocytochemical reaction product took place together with the reduction of synaptophysin-positive granules distribution density in all cortical layers of. At the same time, electron-dense terminals demonstrating early degenerative processes were found. In the neuropil of the neocortex, a sharp decline in the number of growth cones, small processes and forming synapses was accompanied by significant changes of the electron density of synaptic, especially post-synaptic, membranes and densities. In the experimental animals, the number of growth cones and emerging synaptic structures were shown to increase only by postnatal day 10. Thus, the effects of hypoxia in the early postnatal period, causing disturbances of synaptogenesis, persist throughout the whole neonatal period examined.

[Reactive microglial changes in rat neocortex and hippocampus after exposure to acute perinatal hypoxia]

The dynamics of reactive changes of a population density of microglial cells and the reversibility of their phenotypic forms were studied in the brain of neonatal rats at different time intervals after 1 hr-long exposure to acute normobaric hypoxia in the pressure chamber at the second postnatal day. Different areas of the neocortex (frontal, motor, somatosensory and visual) and of the hippocampus (CAI, CA3, CA4 and fascia dentata) were examined 1 hr, 3 hrs, 1 and 5 days after exposure to hypoxia. Microglial cells were demonstrated using an immunocytochemical staining with the monoclonal antibodies against Iba- 1 antigen. The results have shown that the reaction of microglia to acute hypoxia in both the neocortex and the hippocampus of the new-borns developed simultaneously and synchronously with the augmentation of cell death. The increase of a population density of amoeboid form of microglial cells in the brain areas studied was recorded already after 1 hour as a result of their migration from the subventricular region and the areas adjacent to large vessels from where they practically disappeared. The number of amoeboid microglial cells in this area has recovered rather quickly (in 3 hrs). The population densify of microglial cells, especially of amoeboid forms, sharply increased with the augmentation of cell death and remained unchanged for about 5 days.

[Effect of hypoxia in early perinatal ontogenesis on behavior and structural characteristics of the rat brain]

The study has shown the acute hypoxia in newborn rat pups to lead to disturbances of processes of formation of brain structures, behavior reactions, and learning in the subsequent ontogenesis. The single normobaric hypoxia at the 2nd day of life causes retardation of such integrative parameter or genera development and growth as body mass at the period of feeding. In such animals, essential disturbances of the sensorimotor development were revealed in forms of delay of reflex reactions of turning on a plane, negative geotaxis, and avoidance of edge. Also detected was action of hypoxia on hanging on a rope by using front legs (a symptom of muscle weakness). Morphological study has shown stereotypic reaction to the early postnatal action of hypoxia in all studies of all studied functional zones of neocortex - motor, sensomotor, auditory, visual. The death of nerve cells is predominant in the II-III associative layers, the sizes and number of pyramidal neurons are sharply decreased. Different hippocampus fields maturing in mammals show a characteristic response to hypoxia. In individual hippocampus fields there was detected different degree of death of neurons, predominant in the CA3 and CA4 fields. A possibility of modeling of perinatal encephalopathy with minimal brain dysfunctions in children is discussed.

[Participation of serotonin in the mechanisms of the formation of trigeminal motor nucleus]

The formation of trigeminal motor nucleus (TMN) was studied in the early postnatal period in 21 female Wistar rats which received the serotonin biosynthesis inhibitor para-chloro-phenylalanine at prenatal Day 16 (the period of serotoninergic system formation). It was shown that the serotonin deficit during the prenatal period in rats resulted in the changes of TMN structural organization. In the early postnatal period, the delay of neuropil development, the reduction of cell body size with the partial loss of Nissl substance in some of the neurons, the presence of degenerating neurons with the signs of hyperchromatosis in all the parts of the nucleus, especially in TMN ventromedial part, were detected. At later stages, the destruction of motoneurons became slower, though some of them had morphological abnormalities. With the increase of the postnatal age (by Day 20) the number of motor neurons decreased, apparently, as a result of the gradual intensification of cell death. Simultaneously with the motor neuron degeneration in TMN parts studied, the astrocytic gliosis was observed.

[Morphological types of activated microglia in the hippocampus observed following transient total brain ischemia]

The aim of the study was to evaluate, by using immunohistochemistry (demonstration of Iba-1 protein), the morphological features of the rat hippocampal microglia and to describe its cellular types during the response to a single total brain ischemia of 12 min duration. The results obtained suggest the existence of several morphologic types of microgliocytes in the intact hippocampus, while some more types appear in response to ischemic lesion of neurons. These changes in general population of the hippocampal microgliocytes is related to their functional activation. During the post-ischemic period (3, 7 and 14 days following the challenge), there appeared multiple micro-outgrowths of the microglial cell processes, which suggests the enhancement of their interaction with surrounding cellular elements and may be the manifestation of the process of the elimination of neuropil lesioned synaptic structures.

[Synaptogenesis in the dorsal raphe nucleus of rat medulla oblongata in serotonin deficiency]

The purpose of the present study was to examine the synaptogenesis in the dorsal raphe nucleus (DRN) in Wistar rats (n = 8-10 for each time point) in the end of prenatal (days 19 and 20) and early postnatal (days 5 and 20) periods, and to determine the role of serotonin in the formation of synaptic contacts during this period of development. It is shown that at prenatal dayl9 neuropil started to develop in DRN -d, DRN -v and DRN -1 in control (intact) animals, while the synaptic contacts appeared on cell processes. At prenatal day20 synaptic contacts were detected for the first time on neuronal cell body surface. The density of synaptophysin-positive granules on both the cell processes in the neuropil, and neuronal cell bodies was sharply and considerably increased by postnatal day 5. Subsequently, until postnatal day 20, the augmentation of their density was insignificant. Serotonin deficiency in a second half of prenatal development, induced by a single injection of parachlorophenylalanine to female rats at gestational day 16 resulted in a significant delay of synaptogenesis in DRN of their offspring in both prenatal and early postnatal periods. With the increase of postnatal age the density synaptic contacts was unequally augmented in various parts of DRN: in DNR-d it approached the control level, while in DRN-v and DRN-1 it remained significantly reduced. The results received suggest serotonin participation in synaptogenesis in DRN.

[The remote consequences of hypoxia influence in perinatal development period on structurally functional characteristics of the rat brain]

The study has shown that influence of acute hypoxia in perinatal period leads to structural changes in motor and visual of the neocortex for 20 postnatal days in the form of disturbance of the structural organisation of the neocortex layers. Different fields of hippocampus in perinatal period differently react to hypoxia, and evidence of existence of a long-term perinatal hypoxia was obtained. It is established that after action of acute hypoxia in all the fields there is a cellular destruction, and thinning of pyramidal neurones layers. The most expressed cellular destruction takes place in fields CA4 and CA3. In process of augmentation, the destruction of cells remains appreciable in the field CA4, reduced in the field CA3 and not found in the field CA1; however, in fascia dentate, the destruction of granular neurones with age augmentation increases. Along with in reduction of the dimensions of cellular bodies pyramidal neurones in all fields of hippocampus takes place. Also in all fields of hippocampus, activation of astrocytic reaction occurs, more expressed in the field CA4. The hypoxia influence in the early postnatal period can affect synaptogenes, particularly the formation of giant synapses in a dentate fascia. Study of functional features of the excitatory system of such animals has shown that hypoxia can induce appreciable disturbances of behavioural responses. In rats, disturbances of inhibiting functions of the cerebral cortex, raised anxiety, and spatial learning and working memory disturbances have been noted.

Early and delayed effects of hypoxia during the infantile period on behavioral and hormonal reactions of rats

We studied the early and delayed effects of hypoxia during the infantile period on the behavioral reactions and corticosterone concentration in male rats. The elevation of corticosterone concentration, decrease in the immobility time (forced swimming test), and increase in the nociceptive response (formalin test) were observed in 7-day-old rats immediately after hypoxia. Adult animals exposed to hypoxia at the age of 7 days exhibited elevated basal corticosterone level and lengthened immobility time. Hypoxia had the same effect on plasma corticosterone concentration in 7-day-old and adult rats. Changes in corticosterone concentration after forced swimming were shown to differ in hypoxic animals and non-hypoxic specimens. Studying the dynamics of age-related variations in the test parameters will contribute to the understanding of pathogenetic mechanisms and development of new methods for pharmacological correction of postnatal changes in CNS after hypoxia during early ontogeny.

[Fatty acids of phospholipids of brain cell nuclei in rat ontogenesis]

Experiments were carried out on the 19-day old rat embryos, the 5- and 45-day old rat pups, and the 1.4-1.5-year old rats. Phospholipids and their fatty acid composition in brain cell nuclei were studied using methods of extraction, two-dimensional thin-layer chromatography, and spectrofluorimetry. In the course of ontogenesis, the percentage of different classes of nuclear phospholipids was changed; at the postembryonic period, the unsaturation index of lipids (phosphatidylcholine and phosphatidylethanolamine) and the content of unsaturated (especially polyenic) fatty acids decreased. Microviscosity of nuclear membranes increased; this changes were also shown earlier in phylogenesis of vertebrates. Thus, the facts revealed in the present work correspond to the recapitulation law. It is suggested that such change of lipid ratio and of composition of their fatty acids as well as of the membrane microviscosity serve for regulation of functions of membrane proteins and have adaptive character.

[Expression of contractile proteins alpha-actin and myosin of smooth muscle cells and collagen of IV type in human placenta at placental insufficiency in III trimester of pregnancy]

Changes of expression of contractile proteins (alpha-actin and myosin of smooth muscle cell) and of collagen of IV type in stroma of human placental villi were studied at the diagnosed placental insufficiency (PI) in III trimester of pregnancy. The study revealed pronounced disturbances of expression of contractile proteins and collagen of IV type at PI. It is shown that in perivascular envelopes of vessels of stem and intermediate villi there is present a much greater amount of cells expressing smooth muscle actin and myosin. These cells are arranged by the denser concentric layers and more compactly than in norm and fill the intervascular space inside the villi. The width of perivascular envelopes of vessels is higher, while vascular lumens are lower than in norm. In terminal villi the capillary walls are thickened and the number of pericytes immunopositive against the smooth muscle cell alpha-actin and myosin as well as collagen of IV type is increased. The change of synthesis of the cytoskeletal contractile proteins and collagen of IV type is shown to lead to structural disturbances of villi of different types and of perivascular areas and vessels, which doubtlessly indicates their participation in pathogenesis of placental dysfunction and of disturbance of placental hemodynamics.

[Effects of prenatal influences of buspirone and stress on indices of inflammatory pain response and depressive behaviour in adult rats]

New data on complex realization of anxiolytic, antidepressive and antinociceptive effects of prenatal injections of a 5-HT1A agonist buspirone were obtained in prenatally stressed adult rats. Buspirone was injected to female rats from the 9th to 21st days of pregnancy; during the last week of pregnancy buspirone was injected 10 min before immobilization stress. In the adult offspring of both sexes, behavioral indices of tonic pain response in the formalin test and the indices of depression in the forced swim test were investigated. The choice of the target was defined in accordance with available literature data on the role of 5-HT1A receptors in the mechanisms of prenatal stress, of formation of the ascending link of the nociceptive system, of development of depression, and in the mechanisms of the treatment ofnociceptive information. Prenatal stress increased the duration of licking and the time of immobility, the indices of tonic pain and depression in the rats of both sexes. Buspirone evoked the decrease of the indices investigated in prenatally stressed rats in both tests in comparison with the relevant indices in prenatally stressed rats that were not subjected to buspirone. Thereby, it has been demonstrated that buspirone normalized the indices of the tonic pain response modified by prenatal stress; a considerable decrease of the index of depression suggests that there are differences in mechanisms of antinociceptive and antidepressive effects of buspirone. The data on complex realization of anxiolytic, antidepressive and antinociceptive effects ofbuspirone stimulate the attention of clinicians and prompt further investigations in this direction.

[Structural changes in human placenta and its vascular bed in syndrome of placentar failure]

Study of born placentas with chronic functional failure established in the III pregnancy trimester has revealed several characteristic structural alterations of placentar villi and of its vascular bed elements. There has been shown a decrease of the number of terminal villi and an increase of their sizes (approximately 3 times) as compared with norm, a change of transformation of cytotrophoblast into syncytiotrophoblast, thickening of vascular endothelium, a decrease of the number of capillaries-sinusoids, and a decrease of the number of syncytiocapillary membranes, which leads to deterioration of conditions of the maternal-fetal diffuse exchange. It has been established that in placentar failure, expression of the vascular endothelial growth factor (VEGF) by cytotrophoblast cells, syncytiotrophoblast, and Kashchenko-Hoffbauer cells is enhanced as compared with norm, which can be considered a reaction to a decrease of intensity of placentar blood circulation.

[Disturbances in the development of various hippocampal fields in rats as a long-term effect of acute perinatal hypoxia]

The aim of this study was to determine the long-term effects of acute normobaric hypoxia in the perinatal period on the development of a hippocampal formation in rats. The experiments performed have shown that the exposure to hypoxia on postnatal day 2 resulted in a significant damage to the hippocampal field structure. Differential field sensitivity to the damaging factor was also detected. At postnatal day 20, the cell death was found in all the fields and the thinning of pyramidal neuron layers was observed. The neuronal death was mostly expressed in CA4 and CA3 fields. At postnatal day 30, the neuronal death remained significant in CA4 field, while it was reduced in CA3 field and was not found in CA1 field, however, in fascia dentata the death of neurons of the granular layers was increased. Along with it, the dimensions of the pyramidal neuron cell bodies were reduced in all the hippocampal fields. Also, in all the hippocampal fields, the activation of astrocytic reaction was found, which was more expressed in CA4 field, where gliosis was found to remain until prepuberal age (day 30).

[Change of composition of intermediate filaments in cells of rat telencephalon at early period of postnatal ontogenesis]

The goal of the present work was to study composition and spatial-temporal distribution of cells containing various proteins of intermediate filaments (nestin, vimentin, GFAP) in various brain parts at the early postnatal period of rat ontogenesis. By using methods of immunochemical determination of proteins of intermediate filaments it has been established that at they early period of ontogenesis, in the course of maturation of the nervous tissue, in cells of cortex, hippocampus, and subventricular area there occurs a change ofimmunochemical profile of intermediate filaments: the nestin+/vimentin+/GFAP- -cells become the nestin-/vimentin-/GFAP- ones.

[Morphofunctional characteristic of the rat distal spinal cord after its complete experimental section with subsequent treadbun training of the animal]

Motor activity of rats has been studied after complete experimental section of spinal cord at the lower thoracic level. A treadbun training performed one day after the operation has been shown to lead to the appearance of movement of hindlimbs and to restoration of function of support of the body weight. In our opinion, the key moment in initiation of locomotor movements is stimulation of foot. Morphoimmunohistochemical study (detection of nuclear protein of proliferation cells, synaptophysin, and glial fibrillary acid protein) of the lumbar enlargement has allowed revealing reorganization of motoneurons, interneurons, and afferent chain in the distal part of the sectioned spinal cord. In trained animals there are observed the normal structure of motoneurons and the appearance of aggregates of synaptophysin-immunoreactive structures lost after the operation.

Morphofunctional characteristics of the lumbar enlargement of the spinal cord in rats

The topography of the lumbar enlargement of the spinal cord in rats was studied; an immunohistochemical method was used to determine the distribution of synaptophysin--a membrane protein of synaptic vesicles. Synaptophysin-immunoreactive structures were detected in the gray matter of all Rexed laminae, around most neurons and in the neuropil. Previously undescribed subpial synaptic contacts were detected immunohistochemically in the white matter and confirmed by electron microscopy. A non-myelinated component of the corticospinal tract, including axonal varicosities and synaptic contacts, was observed in the dorsal part of the white matter of the lumbar enlargement of the spinal cord.

Vimentin-immunopositive cells in the rat telencephalon after experimental ischemic stroke

The aim of the present work was to perform immunocytochemical studies of cells synthesizing the intermediate filament protein vimentin in the telencephalon of intact rats and rats subjected to unilateral permanent occlusion of the middle cerebral artery, which models ischemic stroke. In the intact rat brain, vimentin-containing cells were seen in the brain barriers. At 14 days from occlusion of the middle cerebral artery, there were numerous vimentin-immunopositive cells in the perifocal damage zone, and these accounted for a significant proportion of the cells in the regenerating nervous tissue at the boundary with undamaged tissue. The subependymal proliferative zone contained a significant number of vimentin-negative small cells, located between the long processes of vimentin-immunopositive cells running towards the lesioned zone. These data provide evidence of the predominant location of vimentin-immunopositive brain cells (in both intact and lesioned animals) in the zones forming barrier structures.