M. A. Kulikov

Behavioral characteristics of WAG/Rij rats susceptible and non-susceptible to audiogenic seizures.

Some rats of the WAG/Rij (Wistar Albino Glaxo from Rijswijk) and Wistar strain are susceptible for audiogenic (convulsive) seizures. In the present study, behavior of susceptible and non-susceptible rats from the WAG/Rij strain, genetically predisposed to absence epilepsy, and outbred Wistar strain, genetically not predisposed to absence epilepsy, was compared to assess the level of anxiety (in the open field, light-dark choice and elevated plus-maze tests) and the level of depression (in the sucrose consumption and forced swimming tests). Increased level of anxiety was found only in audiogenic susceptible rats both from WAG/Rij and Wistar strain, but increased level of depression was found only in WAG/Rij rats independently of their susceptibility to audiogenic seizures. The results suggest that enhanced level of depression in WAG/Rij strain rats is associated with absence epilepsy but enhanced level of anxiety with susceptibility to audiogenic seizures.

Dopamine-dependent nature of depression-like behavior in WAG/Rij rats with genetic absence epilepsy

WAG/Rij rats given placebo showed a depression-like state as compared with normal Wistar rats (lacking convulsive pathology); this was analogous to the state previously seen in rats of this line, with decreased investigative activity in the open field test, increased immobility in the forced swimming test, and decreased consumption and preference for sucrose solution (anhedonia). Chronic administration of the tricyclic antidepressant imipramine (15 mg/kg, i.p., 15 days) had therapeutic (antidepressant) effects on depression-like behavior in WAG/Rij rats. After withdrawal of antidepressant therapy, the behavior of WAG/Rij rats was not significantly different from that of Wistar rats. Acute (single-dose) administration of the selective dopamine D2/D3 receptor antagonist raclopride (100 µg/kg, i.p., 15 min before the start of behavioral testing) increased the symptoms of depression-like behavior and suppressed the antidepressant effect of chronic administration of imipramine in WAG/Rij rats. Raclopride had no significant effect on behavior in Wistar rats. Administration of the dopamine D2/D3 receptor agonist parlodel (a therapeutic form of bromocriptine) cured the depression-like behavior of WAG/Rij rats and had no significant effect on behavior in Wistar rats, with the exception of a reduction in the duration of immobility in the forced swimming test. Imipramine and raclopride had no significant effect on the levels of total movement activity and anxiety in either WAG/Rij or Wistar rats. These results demonstrate the dopamine-dependent nature of depression-like behavior in WAG/Rij rats and show the possible involvement of dopamine D2 receptors in mediating the antidepressant effect of imipramine on genetically determined depression-like behavior in WAG/Rij rats.

Coordination between posture and movement in a bimanual load-lifting task: is there a transfer?

The present experimental series was designed to test the possibility that an anticipatory postural adjustment learned during the performance of a bimanual load lifting task may be transferred between the upper extremities. Eight seated subjects were asked to maintain horizontally one forearm (postural arm) loaded with a 1kg load, which was fixed to the arm by means of an electromagnet. The unloading was triggered either by the experimenter pressing a switch (control) or by the subjects making a voluntary movement with their other arm (moving arm). In the latter case, the subject lifted a 1-kg load resting on a force platform with the moving hand, and the switching off was triggered when the force level reached a threshold of 0.5 kg. The maximum amplitude (MA) and the maximum velocity (MV) of the postural forearm elbow joint rotation occuring after the unloading were measured at each trial. The learning process was estimated by performing a regression analysis on each series of trials, using an exponential model, and from the intercept of the regression curve with the ordinate. 1. During the original learning session (three series of 20 trials), a decrease in MA and MV was found to occur both within the series and between the series during a session. 2. After the initial learning session, the sides of the postural and moving arm were interchanged to test whether any transfer had occurred. The first series of trials in the second session (transfer) and the last series of trials in the original learning session were compared and found to be significantly different in terms of the intercept (seven subjects in the case of MA, five subjects in the case of MV) and the slope (five subjects), indicating a lack of transfer. 3. The data recorded during the second transfer learning session indicated that learning occurred in all eight subjects in the case of MA and in six subjects in the case of MV. It was observed that the original learning session did not facilitate the second one. 4. The lack of transfer of the anticipatory postural adjustment observed in this task is discussed with reference to the data in the literature.

Prophylactic Actions of the Antioxidant Agent AEKOL on Behavioral (Psychoemotional) Disturbances Induced by Chronic Stress in Rats

The studies reported here provide the first evidence that the antioxidant preparation Aekol, which contains a mixture of vitamins A, E, and K3, has antidepressant properties and prophylactic actions in relation to behavioral (psychoemotional) disturbances induced in rats by chronic stress (neuroticization). The behavioral disturbances consisted of a state of depressivity, accompanied by increased anxiety, elimination of individual differences in behavior, and weakening of the relationships between behavioral measures, and these were recorded in the same animals in three different behavioral tests (open field test, forced swimming test, and light-dark selection test).

Spatial Distribution of Coefficients of Asymmetry of Brain Bioelectrical Activity during the Experiencing of Negative Emotions

Significant differences in the spatial distribution of the coefficients of asymmetry of the power of bioelectrical activity were identified in negative emotions of different qualities (anger and grief). In the case of the sthenic (excitable) emotion anger, there was an increase over baseline in the positive value of the coefficient of asymmetry in the anterior areas and the β2 range, while for the asthenic emotion grief, there was an increase in the negative value of the coefficient in the β1 range and a generalized increase in slow-wave activity.

Innate versus learned factors determining limb preference in the rat.

The basic factors determining forelimb preference in the performance of different skilled movements were studied in white rats. To analyse whether limb preference actually reflects an initial individual motor asymmetry or is a result of instrumental learning (the first successful movement becoming fixed), the method of retrograde amnesia from electroconvulsive shock was used. It was shown that limb preference is initial and not a results of learning and, evidently, is due to intrinsic factors. The preferred limb can be identified in as few as 3 successful movements. There is a gradation among animals according to the degree of initial limb preference and its resistance to rearrangement of the motor task. The differences of limb preference in different movements were also analysed. Dependence of the preference on the character of the required movement was shown. Four basic types of movement were revealed by factor analysis. As different muscular groups (distal and proximal), controlled by different descending motor systems can be involved in the performance of different movements, it is assumed that the initial motor asymmetry in each movement is a result of asymmetry of central motor structures involved in the realization of the movement. In the same animal asymmetry of different motor structures might be different. This could explain different limb preference in different movements.

Reorganization of bimanual motor responses on formation of a lateralized food-procuring skill in rats

After 48-h food deprivation,Wistar rats were trained to reach a food sphere from a narrow horizontal feeder tube with one paw, with a free choice of limb. The animals used both limbs at the initial stages of training — seizing of food with one paw could alternate with seizing using the other paw, and both limbs could be involved alternately in movements preceding seizure of food. The dynamics of the reorganization of bimanual movement responses during the training of rats with different motor preferences (right-handed, left-handed) were studied. Bimanual movements in preliminary trials disappeared later than in movements ending with successful food extraction during the acquisition of both right-and left-sided skills. The disappearance of bimanual movements in preliminary trials was regarded as a measure of the maximum extent of lateralization of the skill and establishment of a new motor coordination. During training, left-handed rats reached the maximum level of lateralization of the skill earlier than right-handed rats.

Electroencephalographic and vegetative correlates of the mental reproduction of emotional states

The present investigation is devoted to an analysis of the changes in the bioelectrical and vegetative indices during the mental reproduction of emotional states by man. An analysis of the data of the mapping of intracortical interactions as a function of the time course of the changes in the R-R interval was carried out. Two stages in the mental reproduction of emotions were identified which are characterized by the presence of different centers of integration, in the frontal and temporal divisions of the cerebral cortex. It was demonstrated that in the presence of maximal emotional tension the center of integration shifts from the frontal regions to the temporal region of the left hemisphere.

Changes in spontaneous brain bioelectrical activity during transcranial electrical and electromagnetic stimulation

The systems responses of the brain to therapeutic transcranial electrical and electromagnetic stimulation were studied and the neurophysiological criteria for assessing the efficacy of this treatment were identified using comparative clinical and experimental studies with analysis of spontaneous bioelectrical activity, along with assessment of behavioral and clinical measures. Study groups consisted of six patients with chronic post-traumatic unconscious states during courses of transcranial electrical stimulation and 17 intact Wistar rats subjected to transcranial electromagnetic stimulation. A relationship was found between the effects of transcranial stimulation and the initial level of intercenter interactions of brain bioelectrical activity assessed in terms of coherence. Hypersynchronization of biopotentials, identified as a major element in the reactivity to this type of stimulation, may be of the greatest value in the recovery of patients with cerebral pathology in cases with initially reduced levels of intercenter interactions in the absence of pathologically increased functional connections in the brain.

Characteristics of Learning Voluntary Control of Posture in Lesions of the Pyramidal and Nigrostriatal Systems

The aim of the study reported here was to investigate impairments on the learning of voluntary control of the center of pressures using visual feedback in patients with lesions of the corticospinal and nigrostriatal systems. Participants were 33 patients with Parkinsons disease and 20 patients with hemipareses due to circulatory lesions in the basin of the middle cerebral artery. Subjects stood on a stabilometric platform and used two computer games over 10 days to learn to shift the body relative to the foot to move the centre of pressures, indicated by the position of a cursor on the screen, with the target and to move the target to a specified part of the screen. The games differed in terms of the postural tasks. In one, the direction of movement of the center of pressures was not known to the subjects, and subjects learned a general strategy for posture control; the other formed a strictly defined postural coordination. Both groups of patients were found to have impairments of voluntary control of the position of the center of pressures. There were no differences between groups of patients, in terms of the severity of the initial performance deficit in the task involving shifts of the center of pressures in different directions (the general strategy for controlling the center of pressures), while learning of this task was more difficult for patients with Parkinsons disease. The initial deficit in the fine postural coordination task was more marked in patients with Parkinsonism, though learning in these patients was significantly better than in patients with hemipareses. It is suggested that the mechanisms of involvement of the nigrostriatal and corticospinal systems in learning the voluntary control of posture have elements in common as well as unique elements.