Dynamics of Stability of Orientation Maps Recorded with Optical Imaging.

Orientation selectivity is an important feature of visual cortical neurons. Optical imaging of the visual cortex allows for the generation of maps of orientation selectivity that reflect the activity of large populations of neurons. To estimate the statistical significance of effects of experimental manipulations, evaluation of the stability of cortical maps over time is required. Here, we performed optical imaging recordings of the visual cortex of anesthetized adult cats. Monocular stimulation with moving clockwise square-wave gratings that continuously changed orientation and direction was used as the mapping stimulus. Recordings were repeated at various time intervals, from 15 min to 16 h. Quantification of map stability was performed on a pixel-by-pixel basis using several techniques. Map reproducibility showed clear dynamics over time. The highest degree of stability was seen in maps recorded 15-45 min apart. Averaging across all time intervals and all stimulus orientations revealed a mean shift of 2.2 ±â€¯0.1°. There was a significant tendency for larger shifts to occur at longer time intervals. Shifts between 2.8° (mean ±â€¯2SD) and 5° were observed more frequently at oblique orientations, while shifts greater than 5° appeared more frequently at cardinal orientations. Shifts greater than 5° occurred rarely overall (5.4% of cases) and never exceeded 11°. Shifts of 10-10.6° (0.7%) were seen occasionally at time intervals of more than 4 h. Our findings should be considered when evaluating the potential effect of experimental manipulations on orientation selectivity mapping studies.

[The Dual Nature of the Electrical Signals of the Brain (Electrical and Electrochemical) Which Were Recorded With the Help Polarizable Electrodes From Inert Metals].

In the modern neurophysiology opinion was confirmed that the electrical signals of the brain in the frequency band from DC to electroencephalogram recorded with metallic conductors of inert metal implanted in the brain are formed solely by changes in the electric field of the brain. This paper presents a review of the literature and our own data, according to which the formation of these signals involves two factors. One factor is a change in the charge of the electric double layer electrode having a capacitor property and change the value of its charge with changes in the electric field volume conductor--the brain. Another factor is an electrochemical signal is defined by local changes in the redox potential (E) neuronal-glial populations surrounding the electrode. The paper provides an overviews the electrical and electrochemical properties of the electrodes of the inert metals used in electrophysiology. It is shown that each of these factors has the characteristic parameters over time and amplitude. The data of own studies of local changes in E cortex accompanying brain's response to the implantation of electrodes in the brain's cortex, the natural behavior of animals in the wake-sleep, integrative brain function and effect of pharmacological agents. These results give evidence of the highly informative study of local changes in brain E in order to study energy metabolism in the brain of waking animals, and lay the foundation for the study of local changes in brain energy metabolism in free animal behavior.

Electrophysiological correlations of morphological restructuring in experimental local ischemia of different severity in the rat sensorimotor cortex.

Local cerebrovascular disorders were modeled by reversible photochemical clotting of hemispheric cortical vessels. Mild ischemia led to reversible edema in the surface layers of the cortex: cytotoxic edema of the neuropile, primarily of the distal dendrites. This status led to an increase in the lower delta rhythm frequency band power. After administration of systemic anesthetic, delta rhythm appeared sooner in the ischemic foci than in intact cortical areas. More severe ischemia led to the appearance of dark and pyknotic neurons and reduction of oscillation power in all EEG spectrum bands. Restructuring of primarily dendrites caused by local moderate ischemia of the surface cortical layers at the early stage of neurodegenerative processes stimulated the inhibitory recovery processes.

[The possible role of nitrogen dioxide produced in the field of bifurcation of vessels, in the processes of their damage in hemorrhagic strokes, and the formation of atherosclerotic plaques].

According to modern views the formation of atherosclerotic plaques is associated with accumulation of cholesterol in the vascular wall. This is due to an imbalance between the intake of cholesterol in the intima of vessels, together with the low-density lipoproteins (LDL) and its output with high-density lipoprotein (HDL). Change of LDL (glycosylation, lipid peroxidation, hydrolysis of phospholipids) and the effective release of cholesterol from the endothelium of the vascular wall are the factors that cause an imbalance in cholesterol metabolism. In this paper we propose a new concept of the mechanism of initial formation of atherosclerotic plaques, which can complement the existing concepts. According to this concept an important role in the early stages of atherosclerosis are highly reactive molecules of nitrogen dioxide (NO2), resulting from the violation of the cycles of nitric oxide and superoxide anion radical. Hypothesized that the mechanism of antiradical protection of cells and the organism as a whole, above all, laid out in most of the cyclic organization of metabolic processes that involve the formation of free radicals. Violation of this cyclic mechanism may be one of the causes of many diseases associated with hypoxia/ischemia and inflammation. The review considers the hypothesis of the possibility of participation of NO2 and OH-radicals formed in violation of the cycles of NO and superoxide, in the mechanisms of vascular damage with hemorrhagic stroke and in the formation of atherosclerotic plaques.

Structural changes in dendritic loci and protective effect of neurotrophic factors from the cerebral cortex of animals with favorable outcome of experimental hemorrhagic stroke.

Structural changes in the sensorimotor cortex of the cerebral hemispheres were studied in rats with experimental hemorrhagic stroke in the internal capsule. Changes in the shape and decrease in the density distribution of spines on apical dendrites of layer V pyramidal neurons of the sensorimotor cortex were revealed. Some fractions isolated from the complex of neurotrophic factors of the cerebral cortex of animals with a favorable outcome of hemorrhagic stroke were shown to affect the distal and proximal dendritic loci. As differentiated from the "nonactive" fraction, the "active" fraction improved the behavior of rats surviving hemorrhagic stroke. The density distribution of spines (particularly in the distal region of apical dendrites of pyramidal neurons in layer V of the cerebral cortex) was stabilized after treatment with the "active" fraction. The "nonactive" fraction had a selective effect on the proximal loci.

[Influence of carbon dioxide on the impregnation of the nervous tissue by silver].

It has been shown that 4% carbon dioxide (CO2) in the air above reaction mixture inhibits the initiation of the formation of silver nanoparticles from complexes with biogenic amines (noradrenaline and serotonin). At the same concentration of CO2 in the air above solution of AgNO3, which is used for staining nerve tissues by the method of Golgi, neurons are preferentially stained, whereas at a concentration of 0.06%, vessels and poor neurons are stained. It is suggested that the entry of free silver ions to neurons is due to the inhibition of sites of initiation of silver nanoparticles in vessels at high CO2 concentrations, while the lack of inhibition leads to silver precipitation in vessels at low CO2 concentrations. It can be assumed that, for stable silver impregnation, the concentration of CO2 must be controlled.

[Influence of cortical neurotrophic factors on the neurocytokine production system in acute hemorrhagic stroke].

The mechanism of therapeutic action of cortical neurotropic factors (CNTF) was studied in hemorrhagic stroke. In intracerebral hemorrhage, CNTFs were shown to elevate the level of nerve growth factor mRNA and at the same time, produce no effect on its level in intact animals. The neuroactivating action of CNTF in the acute phase of hemorrhagic stroke was achieved by intranasal administration due to the retrograde axon transport of CNTF molecules along the olfactory nerve fibers to the brain, by passing the blood-brain barrier. It was ascertained that the molecules of tritium-labeled CHTF accumulated in the central nervous system following 20 minutes and the level of label accumulation is proportionally increased after 120 minutes. The pattern of accumulation of the intranasally administered label in the olfactory tract and olfactory bulb proves CNTF transportation along these structures of the nervous system. Therefore, when intranasally administered, CNTFs are able to transport to the central nervous system along the olfactory tract and to enhance the expression of nerve growth factor mRNA in hemorrhagic stroke.

[Procedures for modeling of hemorrhagic stroke].

Hemorrhagic stroke (intracerebral hemorrhage) is a socially significant cerebrovascular disease. Despite high mortality and disability rates, hemorrhagic stroke has been experimentally studied to a lesser extent than ischemic stroke. The modeling of hemorrhagic stroke may be used to solve a number of fundamental and practical problems. The present review deals with the review of the currently available procedures for modeling hemorrhagic stroke.

[Efficacy of cerebrolysin in cerebral hemorrhage model in rats].

The pharmacological efficacy of cerebrolysin (a brain-derived peptidergic drug) was studied in rats with a unilateral hemorrhagic stroke model. Cerebrolysin produces a neuroprotective effect, which is manifested by a decrease in the number of degenerated neurons in the vicinity of hematoma region in acute period and by a reduction of the neuronal loss in the early recovery phase. Besides, the administration of cerebrolysin improves the functional state as judged from the results of neurological and behavioral tests (open field, paw licking, and passive avoidance). A decrease in the hyperactivity in the open field test and the conservation of latent avoidance in the passive avoidance test demonstrate the drug influence on the maintenance of inhibitory processes deteriorated in stroke.

[A comparative study of antistroke activity of the new drug "cerebral" and its fractions in rats].

The effect of the new drug "cerebral" and its fractions 1-3 on the model of bilateral hemorrhagic stroke in white rats was studied with reference to the action of cebrolysin and cerebrolysate-M. With respect to the general functional state, behavioral activity restoration, and morphological data, the most pronounced antistroke action was observed for the cerebral-1 fraction. This fraction was further separated into three subfractions. The most promising test results were obtained for the 1.2 subfraction, which was selected for the further investigation.

[Neurobiological problems of brain ischemia and post stroke epilepsy]. / Neirobiologicheskie aspekty ishemii mozga i postinsul'tnoi épilepsii.

A review. Current literature data concerning pathophysiological mechanisms of cerebral ischemia and poststroke epilepsy are presented. Results of investigations of structural-functional changes in activity of inhibitory inter neurons, mechanisms of brain plasticity, and main components of neuroprotection in ischemia are also discussed. The presented data confirm the current concept of apoptosis and necrosis as a consequence of injuring action of ischemia, the role of excitotoxicity in pathogenesis of ischemia and poststroke epilepsy, and different kinds of plasticity in recovery of brain functions.

[Simulation of local cerebral hemorrhage in different brain structures of experimental animals]. / Metod modelirovaniia lokal'nogo krovoizliianiia v razlichnykh strukturakh golovnogo mozga u éksperimental'nykh zhivotnykh.

A standardized experimental model of intracerebral hemorrhagic stroke in small laboratory animals is developed and advanced for chronic neurobiological studies of normal and pathological higher nervous activity as well as disorders developed after acute hemorrhages. A device is advanced which allows a researcher to destroy appropriate brain structures (tissues and local blood vessels) with necessary precision by four-six rotations of curved stereotaxically inserted mandrel-wire knife and, subsequently, to inject autoblood into the area of the lesion. The advanced model is convenient for the reproduction of lesions in different brain regions (for the purpose of experimental knockouts) in neurophysiological, neuropharmacological, and clinical investigations.

Ultrastructure of synapses in cerebral cortex layer i in rats with low and high resistance to hypoxia.

Quantitative analysis of synapses in layer I of the sensorimotor cortex in rats with low resistance to hypoxia revealed pronounced changes in the number of synaptic vesicles docked at the presynaptic membrane in active synaptic zones under conditions of acute hypobaric hypoxia. In high-resistant animals the number of docked synaptic vesicles under these conditions remained unchanged. In was hypothesized that high sensitivity to hypoxia in low-resistant rats is determined by high reactivity of the synaptic transmission system.

[EEG--indicator of impairment and recovery of the dendrite structure in the plexiform layer of the cerebral cortex]. / EEG-pokazatel' narusheniia i vosstanovleniia struktury dendritov pleksimorfnogo sloia kory mozga.

The connection between EEG spectrum and structural changes of plexiform layer apical dendrites was revealed during the period of recovery from the deep anesthesia. On the initial phase of recovery when the multiply varicose dendritic enlargements are present, an additional peak in EEG spectrum emerged in a delta-band under weak DC action (10 microA); on the late phase of recovery when the structure of the plexiform layer apical dendrites became normal the peak in EEG spectrum under weak DC action emerged in a tetha-band. Thus, by the absence or appearance of the tetha-rhythm in the cerebral cortex in the response to it direct stimulation we can evaluate the morphological condition of the Plexiform layer apical dendrites.

[Structural analysis of the reactivity of the cerebral cortex plexiform layer under the influence of extreme conditions]. / Strukturnyi analiz reaktivnosti pleksimorfnogo sloia kory mozga pri deistviii ékstremal'nykh faktorov.

Using light and electron microscopic studies it was shown that the most sensitive to different extreme factors influence (deep pentobarbital anesthesia, strong DC brain cortex polarization) were the distal parts of apical dendrites of the plexiform layer. That was a selective, non-specific, reversible varicose-like dendritic swelling. The structure of myelin axons, synaptic boutons and astrocytes was unchanged.