The characteristics of the neuronal reactions of the cat somatosensory cortex to a heteromodal complex conditioned signal]

On alert cats the change was studied of the activity of the neurones of the sensorimotor cortical area at instrumental reaction to a simultaneous heteromodal complex stimulus. It was shown that in the projection of distal limb areas a group could be singled out of neurones, which changed their activity in one direction depending on the character of presented signals. In these cells an increase of discharges frequency was observed in response to complex stimulus, consisting of light and sound signals. After the extinction of the motor reaction both to the complex stimulus and to its components neuronal reactions of lesser intensity was recorded, what determined the absence of the motor reaction. This group of neurones had receptive fields localized on distal limb areas, it was activated at fulfillment of the movement of catching the reinforcement and belonged to neurones of the pyramidal tract. The neurones with receptive fields on the whole limb surface or changing their activity at the animal pose change, had variable reactions to positive and differentiation stimuli.     

Microelectrophoretic studies with 2-bromo-α-ergocriptine on dopaminergic neurons in the feline caudate nucleus

The influence of microelectrophoretically applied dopamine and pressure released 2-Bromo-α-ergocriptine (CB 154) on the spontaneous activity of single neurones in the feline caudate nucleus was studied. Two types of dopamine sensitive neurones were found: the spike-rate of the first type was reduced by dopamine, the firing of the other type was facilitated by dopamine. Both types of neurones were influenced by pressure released CB 154. Neurones which were excited by dopamine were excited by CB 154, while with the other type CB 154 resulted only in an amplification of the inhibition by dopamine.     

The morphochemical characteristics of the brain in Wistar rats that differ by open-field motor activity]

By cytochemical and biochemical methods it is established that in rats with low motor activity the increased content of proteins of cytoplasma and nuclei of neurones of the sensorimotor cortex, caudate nucleus and n. accumbens, the increased activity of a number enzymes of oxidizing and protein metabolism in them are combined with a low activity of enzymes of mediator exchange. In the studied formations in rats with high motor activity an increased activity of synaptic and membrane forms of acetylcholinesterase appears at the same level of activity of cholineacetyltransferase in these subcortical formations and at high monoamineoxidase activity in cellular structures of the cortex and in subcortical formations. It is shown that in animals of the same line but differing by the behaviour in the open field, brain formations such as the sensorimotor cortex, caudate nucleus and n. accumbens have their own biochemical properties of the studied characteristics.     

Changes in the neuronal reactions of the substantia nigra to nociceptive stimuli during electroacupuncture

The nature of responses of neurones in substance nigra reticular (SNR) part of cats to nociceptive electrical stimulations and change of these responses under the action of electroacupuncture (EA) in the area corresponding to the Tsui-Sang-Li point in man have been studied. The most of the neurons studied (72.1%) responded to nociceptive stimulation either with excitation of inhibition of the impulsive activity. The EA eliminated or changed the effect of nociceptive stimulation in 73.2% of the SNR nociceptive responsive neurones. Intravenous naloxone administration blocked the effect of EA depending on a dose. A conclusion has been made that the SNR neurones are involved in the modulation of nociceptive transmission and that the EA action is directed to some restoration of the nociceptive disturbed balance between the excitatory and inhibitory processes in the SNR neuronal population.     

The dependence of the neuronal reactions of the sensorimotor cortex to a simultaneous complex stimulus on the level of the differentiation of its components]

On alert animals the change was studied of the neuronal activity of the sensorimotor cortical area of cats brain in dependence on the level of differentiation of the components of simultaneous heteromodal complex stimulus. According to the character of this dependence and a number of other parameters two groups of neurones were singled out in the sensorimotor cortex. It was shown that parameters of reactions of all recorded neurones of the sensorimotor cortex to the positive conditioned signal were the first established after consolidation of the animal conditioned motor activity. In the course of elaboration following parameters changed: expressiveness, intensity, duration and value of latency. Reactions of neurones of both groups to the inhibitory stimuli were stabilized only after consolidation of the habit of differentiation. Responses of the first group neurones changed only by the pattern of discharge, while the responses of the second group neurones could change by expressiveness of response, its sign, duration and value of latency. Oscillations of the differentiation level after finishing of the elaboration of inhibitory conditioned reactions affected only the responses of the second group neurones to complex components.     

Brain antioxidant systems in human methamphetamine users

Animal data suggest that the widely abused psychostimulant methamphetamine can damage brain dopamine neurones by causing dopamine-dependent oxidative stress; however, the relevance to human methamphetamine users is unclear. We measured levels of key antioxidant defences [reduced (GSH) and oxidized (GSSG) glutathione, six major GSH system enzymes, copper-zinc superoxide dismutase (CuZnSOD), uric acid] that are often altered after exposure to oxidative stress, in autopsied brain of human methamphetamine users and matched controls. Changes in the total (n = 20) methamphetamine group were limited to the dopamine-rich caudate (the striatal subdivision with the most severe dopamine loss) in which only activity of CuZnSOD (+ 14%) and GSSG levels (+ 58%) were changed. In the six methamphetamine users with severe (- 72 to - 97%) caudate dopamine loss, caudate CuZnSOD activity (+ 20%) and uric acid levels (+ 63%) were increased with a trend for decreased (- 35%) GSH concentration. Our data suggest that brain levels of many antioxidant systems are preserved in methamphetamine users and that GSH depletion, commonly observed during severe oxidative stress, might occur only with severe dopamine loss. Increased CuZnSOD and uric acid might reflect compensatory responses to oxidative stress. Future studies are necessary to establish whether these changes are associated with oxidative brain damage in human methamphetamine users.     

Motor alimentary conditioned reflexes and delayed reactions in dogs following destruction of the caudate nucleus]

The characteristics of formation and achievement of motor conditioned reactions were studied in seventeen dogs before and after the lesion of head or body of the caudate nucleus. It has been shown that the degree of higher nervous activity disturbances depends on the localization of injuries in the nucleus, and on the complexity of the tests used. The caudate nucleus exerts a modulating effect on the parameters of motor conditioned reflexes and takes a direct part in the structure of delayed reflexes. Lesion of the caudate nucleus body is attended with more serious disturbances of higher nervous activity than lesion of its head.     

Effect of enkephalins on the plasticity of pond snail

The effects of introduction of leu- and met-enkephalins (LE and ME) into the perfusion medium on the characteristics of electrical activity, spontaneous firing and habituation of single neurones to repeated intracellular electrical stimulation were studied on isolated CNS of molluscs. The character, speed, and degree of development of endoneuronal habituation changed significantly after application of LE in 67 per cent of the neurones studied and in 25 per cent of neurones after ME application. As a rule the changes of habituation dynamics occurred at constant levels of membrane potential, excitability, and reactivity of the neurone. LE and ME exerted different modulating effects on the initial electrical activity in 60 per cent of neurones. The obtained data on the independence of the effects of enkephalins on different parameters of activity of one and the same neurone give evidence of a mosaic character of excitable neuronal membrane. A suggestion is made about the possible role of the revealed opiate dependence of the endoneuronal functional plasticity in realization of opiate influences at the behavioural level.     

Effect of fenamin and haloperidol on conditioned activity of neurons of the motor cortex and striopallidal system

The activity of neurones in the motor cortex, caudate nucleus, putamen and globus pallidus was studied during elaboration of motor conditioned reflexes to time in rabbits, treated with 1-amphetamine and haloperidol. Mechanisms of reproduction of cells trace activity in the reflex to time at the omission of trials, reacted to 1-amphetamine by increasing the intensity of reactions in the motor cortex and inactivation in putamen cells. The curve of dynamics of intensity changes of trace discharges in the course of a series of trials omissions remained unaltered only in motor cortex; in the other structures it significantly differed from the norm of intact animals. Haloperidol depressed the mechanisms of reproduction of trace reactions of the globus pallidus cells, and made them almost fully inactive in the motor cortex; the putamen neurones reacted to haloperidol by an increase of trace reactions intensity. Against the background of the animal chronic 1-amphetamine intoxication, haloperidol normalized the dynamics and intensity of trace activity. "Therapeutic" effect of haloperidol was most distinctly expressed in the motor cortex and putamen cells, less--in the caudate nucleus and was completely absent in the globus pallidus.     

Neuronal impulse trains of the visual and sensorimotor areas of the rabbit neocortex in calm wakefulness and pseudoconditioning

The conjugation of unit activity in the neocortical visual and sensorimotor areas during calm wakefulness and in intersignal intervals, in two groups of rabbits at pseudoconditioning was studied. The first group was presented in a random order with flashes and electrocutaneous stimuli, the second one--with sounds and electrocutaneous stimuli. The number of neurones pairs working in correlation during calm wakefulness is significantly less (35%) than during pseudoconditioning (49 and 50% in the first and second rabbits groups, respectively). During calm wakefulness and in both groups during pseudoconditioning, the number of pairs with delays of discharges of the visual area neurones after the sensorimotor one, and of the sensorimotor after visual up to 120 ms was equal. Comparison of the data on delayed neuronal discharges during calm wakefulness and pseudoconditioning with those obtained earlier with conditioned reflexes testifies that forestalling of visual area neuronal discharges by sensorimotor discharges is characteristic only for the activity of cortical projections of conditioned and unconditioned stimuli.     

The neuronal activity of the medial wall of the frontal cortex in rats at various stages of learning

Unit activity of the medial wall of the rat prefrontal cortex was studied during delayed response of spatial choice. Recording was performed in two groups of animals at different levels of learning. Several types of spatio-selective neurones were revealed. Probable relationships of unit activity changes and level of learning are discussed.     

Dynamical changes and temporal precision of synchronized spiking activity in monkey motor cortex during movement preparation.

Movement preparation is considered to be based on central processes which are responsible for improving motor performance. For instance, it has been shown that motor cortical neurones change their activity selectively in relation to prior information about movement parameters. However, it is not clear how groups of neurones dynamically organize their activity to cope with computational demands. The aim of the study was to compare the firing rate of multiple simultaneously recorded neurones with the interaction between them by describing not only the frequency of occurrence of epochs of significant synchronization, but also its modulation in time and its changes in temporal precision during an instructed delay. Multiple single-neurone activity was thus recorded in monkey motor cortex during the performance of two different delayed multi-directional pointing tasks. In order to detect conspicuous spike coincidences in simultaneously recorded spike trains by tolerating temporal jitter ranging from 0 to 20 ms and to calculate their statistical significance, a modified method of the 'Unitary Events' analysis was used. Two main results were obtained. First, simultaneously recorded neurones synchronize their spiking activity in a highly dynamic way. Synchronization becomes significant only during short periods (about 100 to 200 ms). Several such periods occurred during a behavioural trial more or less regularly. Second, in many pairs of neurones, the temporal precision of synchronous activity was highest at the end of the preparatory period. As a matter of fact, at the beginning of this period, after the presentation of the preparatory signal, neurones significantly synchronize their spiking activity, but with low temporal precision. As time advances, significant synchronization becomes more precise. Data indicate that not only the discharge rate is involved in preparatory processes, but also temporal aspects of neuronal activity as expressed in the precise synchronization of individual action potentials.     

Tryptophan-5-hydroxylase activity in the rabbit brain synaptosomes at different times after the single administration of the opioid peptide Tyr-D-Ala-Gly-Phe-NH2

The activity of the key enzyme of serotonin biosynthesis--tryptophan-5-hydroxylase (T-5-H) was investigated in the synaptosomes of the motor cortex and caudate nucleus of the rabbit brain 30 min or 5 days after single injection of opioid tetrapeptidamide Tyr-D-Ala-Gly-Phe-NH2 (TPA). TPA was injected subcutaneously at a dose of 500 micrograms/kg of rabbit body weight. T-5-H activity in caudate nucleus synaptosomes was two times higher than that of the motor cortex synaptosomes and accounted for 159.67 and 80.84 pmoles of formed 5-hydroxytryptophan/mg protein per hour. 30 min after single injection of TPA the enzyme activity in the synaptosomes of the motor cortex and caudate nucleus decreased by 64.0 and 43.0%, respectively. 5 days following single TPA injection T-5-H activity in the motor cortex synaptosomes increased by 68.4% and in caudate nucleus synaptosomes decreased by 35.6%. Thus, it was established that TPA displayed a pronounced effect on T-5-H activity. The delayed effect of opioid TPA on T-5-H activity was discovered which was manifested on day 5 after the single injection. Possible mechanisms of TPA effect on T-5-H are discussed.     

Temporal organization of interneuronal relations in the cerebral cortex of the cat in relation to the level of alimentary motivation

By means of records of multicellular activity, interneuronal relations and their modifications in two cortical zones (Visual and motor) were studied in cats at different levels of alimentary motivation. For quantitative evaluation of interneuronal relations the statistic method of cross-correlation analysis of impulse trains was used in determining the probability of the appearance of the discharge of one neurone after the impulse of the other one. For groups of neurones in both investigated cortical areas, three-neurones microsystems were singled out and their activity was analyzed by temporal parameters of interaction between neurones at the interval of 120 ms, both within one microarea (intraanalyzer connections) and between microareas of two cortical zones. The correlation of temporal parameters of interneuronal connections (temporal delays in the activity of neuronal pairs) changed depending on spatial localization of neurones and functional condition of the animals. The existence is suggested of "informational" (1-30 ms) and "motivational" (90-120 ms) values of interneuronal relations for interanalyser connections.     

Effect of microelectrophoretically applied acetylcholine, noradrenaline, dopamine and serotonin on the discharge of paraventricular oxytocinergic neurones in the rat

The effects of microelectrophoretic applications of neurotransmitter substances and their antagonists on the activity of paraventricular oxytocinergic neurones were studied in urethane anesthetized lactating rats. Oxytocinergic neurones were identified by their antidromic response to the stimulation of the neurohypophysis and by their characteristic high frequency discharge of action potentials approximately 15-20s before reflex milk ejection. Acetylcholine (ACh) excited the majority (75%) of paraventricular oxytocinergic neurones, and none of the cells was inhibited in its activity by ACh. In about half of the oxytocinergic cells, atropine and hexamethonium reduced the number of action potentials during the burst discharge preceding reflex milk ejection. Noradrenaline (NE), dopamine (DA) and serotonin (5-HT) reduced the activity of most (75-100%) of oxytocinergic neurones, and none of the cells was excited by these catecholamines. These results suggest that paraventricular oxytocinergic neurones receive excitatory cholinergic inputs and inhibitory noradrenergic, dopaminergic and serotonergic inputs.     

The effect of the acute administration of ethanol on the realization of behavior and its neuronal support

In experiments on rabbits trained to instrumental food procuring behaviour it was cleared up, which changes of activity of neurones of the limbic cortical area corresponded to disturbances of this behaviour (increase in time of realization and in the number of errors) caused by intraperitoneal injection of 12% ethanol solution in a dose of 1 g/kg. In comparison with control (administration of isotonic solution), the number of active cells singled out in the microelectrode track was reduced by 1/3; the pattern of behavioural specialization of neurones involved in provision of the disturbed behaviour was changed. The content of neurones of the most recent systems formed during animals learning instrumental behaviour, decreased from 27 to 11%, and of neurones providing for realization of systems formed at previous stages of individual development increased from 18 to 36%.     

电刺激尾核对兔视前区羟戊甲吗啡敏感神经元自发放电的影响

本实验运用多管微电极离子微电泳技术,观察到电刺激家兔尾核头部能影响视前区神经元的自发放电活动。电刺激尾核对视前区羟戊甲吗啡敏感单位的抑制率比较高(P<0.02);微电泳纳洛酮能阻断电刺激尾核的抑制效应,但不能阻断兴奋效应,提示这种抑制效应与视前区内阿片肽的活动有关。但未能看到电刺激尾核的效应与微电泳去甲肾上腺素的效应之间的相关关系。 进一步的观察及统计分析表明,电针及电刺激尾核对视前区羟戊甲吗啡敏感单位的共同抑制率明显高于羟戊甲吗啡不敏感单位(P<0.05),提示视前区的一部分羟戊甲吗啡敏感神经元,可能是这两种刺激的共同作用点之一。     

Characteristics of the neuronal reaction of the substantia nigra to nociceptive stimulation

The nature of neurone response of substance nigra (SN) to nociceptive stimulation of the cat's peroneal nerve has been studied. The recording of neurone SN firing rate revealed that the majority (71.0%) of the SN neurones responded to the nociceptive repetitive stimulation of the peroneal nerve. But the thresholds of nociceptive activation in SN neurones turned to be very high. As a result of it the number of SN neurones responding to repetitive peroneal stimulation was twice as many as the number of cells responding to single stimulation of the nerve. The intravenous injection of naloxone in dose 1.0 mg/kg changed both excitatory and inhibitory responses in majority (71.4%) of SN neurones responding to repetitive peroneal stimulation. Naloxone did not modify the firing rate of neurones nonresponsive to nociception.     

Effect of pentobarbital on neurones in the reticular formation of the brain stem: ionophoretic study in the rat

The effect of ionophoretically applied pentobarbital (PB) upon neurones in the nucleus reticularis gigantocellularis of the rat was studied. PB applied through a micropipette depressed the spontaneous activity of 81% of the neurones tested; the remaining neurones did not change their firing rates. Regardless of current intensities used for PB ejection (5-60 nA) there was no increase in the firing rate during PB administration. The depression was dependent upon both the control firing rate and the PB dose; a total depression of activity was observed at currents between 40 and 60 nA. EC50 (15.5 nA, about 5 X 10(-5) mol.l-1--the drug concentration was approximated theoretically) was assessed from the dose-response curve. Repeated application resulted in a shift of EC50 towards higher current values (desensitization). The Hill coefficient was calculated in conformity with the classical theory. From its value (1.4), it may be assumed that the occupation of only one subunit of the binding site is enough to give a response. Possible mechanisms of action of PB upon neurones are discussed.     

The modelling of theta rhythm regulation by an increasing afferent inflow in septal slices in vitro

The aim of the work was the modelling in vitro of the condition of increased afferent inflow, which in the intact septum results in an increase of population of theta-bursting units, their synchronization and shift to a higher frequency of the bursts, with corresponding changes in the hippocampal electrical activity. Neuronal activity was recorded extracellularly in the medial septal nucleus and vertical limb of the nucleus of diagonal band (MS-DB) in guinea pig septal slices. Electrical stimulation in the medial part of horizontal limb of DB evokes initial period of suppression of spontaneous activity in 85% of the neurones. This low-threshold, rapid inhibition has variable duration (20-280 ms) in different units at low intensities of the stimulating current. With increased intensities of stimulation this inhibitory phase in majority of units is gradually or by steps shortened, though in some units with initial short inhibition it is not changed. As a result the variability of initial inhibitory period between units is decreased and centered around 30-60 ms. Many units with single-spike background activity developed postinhibitory burst responses at various levels of stimulating current. The spontaneously bursting MS-DB units always responded by resetting of their background bursts. In total 58% of all recorded neurones generated evoked bursts under condition of increased afferent inflow.