[Adaptive function of the brain and problems of hypoxia].

Based on the findings of various authors and own experimental data it was concluded that adaptive behaviour is regulated by changing in the level of spontaneous neuronal activity. Spontaneous firing is monitored by brain metabolic M-cholinergic reaction which increased the efficacy of dendritic propagation by mechanism of K+ membrane channels blockade. High energy demands of cholinergic process creates a threat to nerve cells survival in hypoxic conditions.

[The positive effect of short-term haloperidol administration on the dysfunction of brain metabolism and neuronal activity].

Chronic amphetamine injection increased spontaneous neuronal activity in sensomotor cortex and decreased spike activity in caudate nucleus. The neuronal ability to perform the conditioned reactions was greater in the cortex and smaller in the nucleus caudatus. By biochemical investigations it was showed the hyperactivity of dopaminergic system in the caudate nucleus compared to that in sensomotor cortex.

[Glial satellites as the source of additional energy supply to the neurons during the increased frequency of firing activity].

Using surviving slices of guinea pig somatosensory cortex, it was shown that functionally different regulation of spontaneous firing activity in different neurons corresponded to irregular distribution of glial satellites. Maximal increase of spike activity induced by acetylcholine (up to 36 spikes per second) was detected in "silent" neurons which account for 37.2% of nerve cells in layer V.

[Spontaneous activity of cortical neurons in vitro and its regulation under the effect of acetylcholine].

In somatosensory cortical slices it was obtained that neuronal firing excitation evoked by iontophoretically applied acetylcholine was depended on the rate of spontaneous activity. The spontaneous firing rate was regulated simultaneously with dendritic properties and expression of cholinergic reaction. All of these findings may be a reflection of changing in K+ membrane permeability.

Levels of spontaneous activity and spike responses of cortical neurons to local administration of excitatory amino acids to their dendrites and bodies.

Studies of cortical cortex slices showed that spontaneous neuron activity depended on the conditions of transmission of excitation from dendrites to the body. Studies using a measure of the efficiency of dendrosomatic conduction showed that cortical neurons constituted a significantly heterogeneous population. Spike reactions to direct excitation of cell bodies were relatively stable in neurons with different levels of spontaneous activity.

[Spontaneous activity level and spike responses of cortical neurons to local supply of amino acids for dendrites and soma].

In guinea-pig parietal cortex slices, it was shown that neuronal spontaneous activity depended on dendro-somatic propagation of excitations evoked in dendrites. The functional dendritic properties are essentially non-uniform in the population of cortical neurons. Spike responses to direct soma activations are quite stable among neurons with various levels of spontaneous activity.

Characterization of formation and trace rhythm reproduction by rabbit hippocampal neurons during early and late ontogeny.

The formation and reproduction of memory traces by hippocampal neurons were studied and a relationship between the number of presented series of periodical electrocutaneous stimulation and degree of trace acquisition of the rhythm, on the one hand, and rabbit age (6-30 days, 1, 4-5, and 7 years), on the other, was detected. The hippocampus of 6-7-day and 7-year-old rabbits is characterized by low neuron activity and inability to trace acquisition of rhythm. The pulse frequency and trace acquisition of the rhythm in animals aged 8-14 days and 4-5 years (middle age) formed slower than in adult animals (after 2-4 stimulation series on days 2-4 of experiment) and could not be reproduced on the next day without reminding.

Spontaneous activity and rhythm assimilation reactions in baby rabbit hippocampal neurons during learning: age-related characteristics.

The neural mechanisms of the age-related characteristics of memory formation were studied in experiments based on a model providing an analog of a conditioned reflex to time: trace assimilation of the rhythm with which neurons in hippocampal field CA1 were stimulated, in rabbits aged 1-4 weeks and 5-6 months. Stages of changes in neuron spike activity characteristic for developing animals were described. In animals studied one week after birth, there was a predominance of silent cells and cells with low spontaneous activity.

[Spontaneous activity of hippocampal neurons and stimulation rhythm acquisition in young rabbits during learning: age features].

Ontogenetic mechanisms of memory formation were studied using an experimental model of conditioned reflex to time, i.e., trace acquisition of a stimulation rhythm by hippocampal CA1 neurons of young (1-4 weeks old) and adult rabbits (5-6 months old).

Age-related structural and functional characteristics of rabbit hippocampal neurons during the formation of temporal associations.

Spectral analysis (spectral density histograms) of neuron spike activity in the hippocampus of rabbits of different ages revealed trace assimilation of rhythms--an analog of a conditioned reflex to time--after rhythmic stimulation. An association was established between the number of series of periodic electrocutaneous stimulation presented and the extent of trace assimilation of the rhythm, depending on the age of the animal. Trace assimilation of rhythms occurred more slowly in older animals (aged 54-65 months) than in young animals (aged up to one year), predominantly on days 2-3 of experiments after presentation of 2-4 series of rhythmic stimulation, and persisted in a small proportion of cases on the day following stimulation.

Effects of temperature on the spike activity of cortical neurons in guinea pigs.

Studies on parietal cortex slices from guinea pigs showed that a decrease in temperature from 37 degrees C to 24 degrees C significantly decreased the level of spontaneous neuron activity, while activatory reactions to iontophoretic administration of glutamate showed no significant change.

[Age-specific morphological-functional characteristics of the rabbit's hippocampal neurons during conditioning].

Formation of trace rhythm recruitment (an analogue of conditioned time reflex) was studies in CA3 hippocampal neurons of alert young (less than one year), old (54-65 months), and very old rabbits after a prolonged (10-20 min) electro-cutaneous stimulation of a forelimb with the frequency of 0.5-1 Hz. Comparative analysis of neuronal spike activity in young and old rabbits showed that in the late ontogeny the number of spontaneously active neurons was significantly decreased, the proportion of slowly firing neurons increased, the interspike intervals and intervals between spike groups became longer, the number of spikes in a group reduced.

[Effect of temperature on impulse activity of cortical neurons in guinea pigs].

The temperature change of incubating fluid from 37 to 24 degrees C results in significant decrease of neuronal spontaneous firing rate in parietal cortex slices. Evoked spike responses to microiontophoretic application of glutamate practically did not change.

Spike responses of neurons in the motor area of the cortex of elderly rabbits to specific stimuli.

The spike responses of neurons in the motor area of the cortex to tactile and electrocutaneous stimulation of the forelimb were studied in elderly (aged 6-7 years) rabbits. In comparison with young rabbits, the cortex of adult animals contained fewer cells responding to afferent stimulation. The activatory responses of neurons in elderly animals showed smaller increases in the spike frequency from the baseline level.

Morphochemical features of plastic rearrangements of hippocampal neurons after rhythmic stimulation of the limbs in elderly rabbits.

The process of aging is accompanied by significant derangements to brain function, which are expressed particularly as the well-known phenomenon of memory disturbance [4,5]. Since memory functions are based on plastic rearrangements, in which the key role is played by metabolic processes, we elected to study the interactions between nerve cell activity and the state of protein biosynthesis during the formation of temporal associations in animals of different ages [3]. An interferometric method was considered appropriate in this regard as a method for estimating the dry weight of the cytoplasm and nucleus in neurons; this serves as a measure of their protein contents [1,2].

[The spike reactions of the motor cortex neurons of old rabbits to specific stimuli].

Spike reactions of motor cortex neurons to tactile and electrocutaneous stimulation of a forelimb were studied in aged (6-7-year old) rabbits. As compared with young adult animals, the neuronal reactions to afferent stimuli were rarely recorded in the motor cortex of aged rabbits (66.7 and 50%, respectively).

[The morphochemical characteristics and plastic restructurings of the hippocampal neurons after rhythmic stimulation of an extremity in old rabbits].

The rhythmic activity of CA1 hippocampal neurons was studied after the rhythmic (1-2 Hz) electrocutaneous forelimb stimulation (10-20 min) of 6-84-months-old rabbits. The spectral analysis of neuronal activity revealed the age-dependent decrease in ability to reproduce the rhythm of stimulation. The cytochemical data showed that the protein synthesis in the neurons under study also declined with age.

Some physiological characteristics of motor cortex neurons of aged rabbits.

Neurophysiological alterations occurring in the motor cortex of aged rabbits have been examined. Experiments were performed on rabbits of three age groups: one year old (young), four to five years old (middle-aged) and six to seven years old (aged). Extracellular unit activity was recorded in the motor projection of a forelimb.

[The functional and morphochemical characteristics of the hippocampal neurons during the formation of trace processes in old rabbits].

Trace rhythmic activity of dorsal hippocampal neurons were studied after the long-lasting (10-20 min) rhythmic (0.5-2 Hz) electrocutaneous stimulation of the forelimb in alert young (5-7 months), middle-aged (54-65 months), and very old (66-84 months) rabbits. During aging the number of spontaneously active neurons was shown to be significantly decreased, the proportion of slowly firing neurons to be increased, the interspike intervals and intervals between spike groups to lengthen, and the number of spikes per a group to be reduced.

The morphofunctional characteristics of neurons of the sensorimotor cortex of aged rabbits during the trace assimilation of rhythm.

The formation of trace rhythm assimilation (an analog of the conditioned reflex to time) by neurons of the sensorimotor cortex in response to prolonged (10-20 min) electrodermal stimulation of an extremity at a frequency of 0.5-1 or 2 Hz was investigated in awake adult (5-7 months), old (54-65 months), and very old (66-85 months) rabbits. The data of the spectral analysis of the impulse activity of 460 neurons showed aged-related differences in the formation of trace rhythm assimilation by neurons: it takes place after one to two series (1st to 2nd days of the experiment) in young animals; after two to four series of periodic stimulation (2nd to 3rd days of the experiment) in the old animals; in very old animals rhythmic stimulation essentially did not result in rhythm assimilation by cortical neurons.

Characteristics of the trace reproduction of rhythm by neurons of the sensorimotor cortex of rabbits in the aftermath of periodic stimulation.

The trace recruitment of rhythm (TRR), an analog of the CR to time, which arises in response to prolonged electrodermal stimulation of the forelimb of the awake rabbit at a frequency of 0.5-2 Hz, was studied. The activity of 180 cells of the sensorimotor cortex before (80) and after (100) periodic stimulation for a duration of 10-20 min was recorded.

Cholinosensitivity as an indicator of functional differences of neurons of the cortex of young and old rabbits.

The cholinosensitivity of neurons of the motor cortex of young and old rabbits was studied. It was shown that muscarinic activation in the cells of old animals is encountered half as often than in young animals. The age-related decrease in cholinosensitivity is explained by an insufficiency of the overall activation of neurons in old animals.