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Biomedical subjects

F V Kopytova

Publications and source records attributed to F V Kopytova.

At least 19 recordsLinked to original sources
PubMed1994

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. Several sessions of rhythmic (2 Hz) electrocutaneous stimulation were delivered to contralateral forelimb. The neuronal activity was recorded before and after rhythmic stimulation. We also measured the firing rate during spontaneous electromyogram activity of the extensor carpi radialis. Neurons having slow spontaneous firing activity were predominant in aged rabbits as compared with young animals. In young animals the highest values of spontaneous firing rate (15-20 impulses/s) were observed in neurons related to movement. In aged rabbits spontaneous firing rate of movement-related neurons did not exceed 16 impulses/s. During spontaneous movements of extensor carpi radialis, the level of neuronal activity in young rabbits was twice as high as that in aged ones. In young rabbits after rhythmic electrocutaneous stimulation of a forelimb, 20% of recorded neurons exhibited periodic fluctuations in firing rate with the period of preceding stimulation. The repeated stimulation sessions increased the number of rhythmic firing neurons to 40-50%. In aged rabbits, patterns of firing activity of motor cortex neurons did not change significantly after several sessions of rhythmic electrocutaneous stimulation. Decreased neuronal excitability may be the cause of functional alterations in motor cortex neurons of aged rabbits.

Aging↗
PubMed1981

[Changes in the sign of the response of striopallidal neurons during elaboration of conditioned reflexes to time].

During formation of motor conditioned reflexes to time (CRT) in alert rabbits, an increase in the number of neurones with activation and diminution of the number of cells with inhibitory trace activity was revealed when the stimuli were omitted, as compared with conditioned reactions (CR) to actual stimuli pairings, as well as a change in CR and CRT signs, as compared with the sign of cell responses to control tests. The changes were more pronounced in the caudate nucleus and the putamen. In the caudate nucleus and the globus pallidus, the number of cells capable of CRT in omissions of pairings increased as compared with the number of neurones which elaborate CR to actual pairings. Differences in the CR and CRT signs may suggest a difference in mechanisms of consolidation and reproduction of trace processes during elaboration of a motor behavioural act.

Animals↗
PubMedDate not supplied

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. The first series of rhythmical stimulation led to a brief TRR of the stimulation frequency; subsequent series formed a clear TRR which was preserved for several days. The possibility of "retraining" the neurons given a change in the rhythm of stimulation was identified. The capacity of the TRR phenomenon for extinction, prolonged maintenance, and reproduction of traces, as well as "retraining" allies it with processes analogous to the temporary connections.

Animals↗
PubMedDate not supplied

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. Quantitative and qualitative morphological changes in nerve and glial cells in the sensorimotor cortex of old rabbits as compared with young rabbits were identified. It is hypothesized that deviations in the course of mnestic processes observed in animals during aging may be associated with destructive phenomena in the neocortex during normal aging.

Aging↗
PubMedDate not supplied

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. The change in the functional state of the cells of the motor cortex leads to the fact that the frequency of impulse activity of neurons associated with movement proves to be insufficient for the achievement of effective cortical control of motor functions.

Acetylcholine↗
PubMedDate not supplied

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 aim of the present work was to identify the relationship between the process of impressing the assimilation trace of a rhythm during the acquisition of an analog of a conditioned reflex to time in hippocampal neurons and their morphochemical parameters in elderly rabbits.

Action Potentials↗
PubMedDate not supplied

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. Long-latency, slow activatory responses, which were not characteristic of cortical neurons in young animals, appeared; the pattern of these responses could be partially corrected by administration of acetylcholine in the vicinity of the neurons being recorded. The parameters of inhibitory responses were enzyme of the significantly different in animals of different ages.

Acetylcholine↗
PubMedDate not supplied

[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.

Aging↗
PubMedDate not supplied

[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 activation manifested in increasing firing rate over its spontaneous level was less intensive than in young animals. The neuronal reactions of aged animals were characterized by the slower activation with longer latencies and slower development of spike responses. The parameters of slow activation could be partly corrected by the iontophoretic application of acetylcholine to the soma region. Neuronal inhibition recorded in the motor cortex of aged rabbits was not markedly changed compared to inhibition reactions in young animals. It is suggested that impairment of the functional state of dendrites in aging is responsible for the changes observed.

Acetylcholine↗
PubMedDate not supplied

[Trace reactions following combination of a sensory stimulus with polarization of the visual region of the cortex].

Spontaneous activity and responses to photic flashes and tones of 133 neurones were recorded in the visual cortex during polarization of the same area (1.5 to 10 muA, 5 to 30 min) and after it (one to 52 min). Responses of cells to two unimodal stimuli of different parameters were analysed, of which one was presented repeatedly during the polarization ("positive"), and the other one to three times ("negative"). Depending on the previous "learning", 47.4% of the units responded after the polarization to "positive" photic stimulus and 37,8%--to acoustic stimulus. The trace effects of the stimuli pairings are reproduced in polarization after-effect by the action of the sensory signal alone. The recorded differences in the nature and duration of the reproduction of trace processes formed to an adequate and inadequate stimuli, are due to the dissimilar action of polarizing currents on neurones of the cortex cross-section and to different effectivity of the visual and non-visual influences related to it.

Acoustic Stimulation↗
PubMedDate not supplied

[Conditioned responses to time of hypothalamic neurons. The ventromedial nucleus].

Conditioned reactions to the time of regularly (every 30 sec.) presented pairings of an acoustic and an electrical cutaneous stimuli were studied in neurones of the hypothalamic ventromedial nucleus in an alert rabbit. Conditioned reactions of an inhibitory (81%) and activating (19%) types were elaborated in 27 out of 63 units (43%). They were significantly reproduced at six to nine omissions of stimulations at the stage of the 50th to 70th pairings. The maximum manifestation of trace processes coincides with the initial formation of a vegetative (electrocardiogram) component of the behavioral conditioned reflex to time. Significant correlation has been shown between the frequency of spikes in the pairings and their omissions, and the corresponding changes in heart rate at the same temporal intervals. This testifies to the involvement of the ventromedial nucleus structures in the formation of the vegetative component of the behavioral conditioned reflex to time. Common characteristics and peculiarities of conditioned reactions to time have been revealed in units of the hypothalamic ventromedial and perifornical nuclei in accordance with morpho-functional properties of the examined structures.

Animals↗
PubMedDate not supplied

[The characteristics of trace rhythm reproduction by the neurons of the rabbit sensorimotor cortex in the aftereffect of periodic stimulation].

Trace rhythm recruitment (TRR)--CR analogue to time was studied appearing in response to prolonged electrocutaneous stimulation of the forelimb of the alert rabbit with the frequency 0.5-1-2 Hz. The activity was recorded of 180 cells of the sensorimotor cortex before (80) and after (100) periodical stimulation during 10-20 min. The first series of rhythmic stimulation led to a short-term TRR of the stimulation frequency, the following series formed a clear TRR, preserved for several days. The possibility was revealed of "relearning" of neurones at stimulation rhythm change. The ability of TRR phenomenon of extinguishment, prolonged preservation and reproduction of traces, "relearning" brings it nearer to the processes, analogous to the temporal connection. The ability to reveal distinctly and to quantitatively estimate the characteristics of the applied stimulus fixated by the neurones, makes this model perspective for comparable study of the memory traces at the neuronal level in the animals of various ages.

Action Potentials↗