Effects of ketamine on neuronal epileptiform responses in the cat neocortex

The effects of ketamine, an antagonist of NMDA receptors, on the neuronal epileptiform responses evoked by applications of strychnine, penicillin, or bicuculline to the suprasylvian gyrus were studied in cats. Ketamine either exerted no effect, or slightly decreased interictal high-amplitude depolarizing shifts of the membrane potential and depolarizing afterpotentials, which appeared spontaneously or were evoked by intracortical stimulation. Repetitive electrical stimulation of the epileptogenic cortical regions resulted in the appearance of autogenerated ictal activity lasting up to several tens of seconds; this activity was produced against the background of a depolarization of neuronal membranes. After ketamine injections, such stimulations evoked no ictal activity in the neurons, or the discharges became much shorter. The results of our study show that the NMDA-dependent postsynaptic components play a more important role in the development of neocortical ictal activity compared with the interictal activity.Neirofiziologiya/Neurophysiology, Vol. 27, No. 1, pp. 32–35, January–February, 1995.     

Interrelationship between vitamins and cytokines in immunity

Cytokines are important proteins that modulate immunity and inflammation. Vitamins are also involved in immunity and inflammation. They are found to restore the ability of some cells to produce certain cytokines. Vitamin deficiency appears to affect the mechanism of immune cells, though the impact of reduced cytokine response in vitamin malnutrition is not clear. Vitamin D is involved in many medical conditions, such as infections and inflammation, and mediates innate immunity. Deficiency of vitamin D increases the risk of infectious and inflammatory diseases. In addition, this vitamin modulates Treg function and IL-10 production which is important for therapeutic treatment. Vitamin A increases inflammatory response and is involved in tissue damage; moreover, vitamin A is a key modulator of TGFbeta which can suppress several cytokines. Vitamin E, an anti-ageing compound, is associated with a defect of naive T cells and may inhibit some inflammatory compounds such as prostaglandin generation.     

Conditioned reflex analysis of functional connections between the hippocampus and limbic system structures

Instrumental defensive conditioned reflex elaborated in dogs to stimulation of the dorsal and ventral hippocampus, also appeared, due to generalization, in response to stimulation of a number of limbic structures. Two types of changes in the generalization effects (estimated by parameters of motor conditioned reaction) were observed in the course of conditioned reflex stabilization: enhancement (in response to stimulation of the lateral hypothalamus, lateral nucleus of septum, limbic cortex) and weakening toward complete disappearance (in response to stimulation of the medial nucleus of amygdala and medial hypothalamus). Manifestation of the generalization phenomenon from the brain structures, which are not involved initially into conditioned activity, suggests the existence of close functional connections between these structures and the hippocampus.     

The limbic system and culture

The human ability to live according to learned, shared rules of behavior requires cortical functions. Is the limbic system also necessary for culture or are its functions opposed to it, requiring cortical inhibition? The sizes of monkey and ape neocortical and major limbic structures scale with brain weight, but the neocortex expands more (has a steeper exponent) than limbic structures. As the human brain evolved it did not deviate from the scaling relationships found in nonhuman anthropoids. This evidence for conservation in scaling supports the idea that limbic functions are necessary for human symbolism and culture.     

Interrelationship between the Bcg and Tbc-1 genes

The relationship of the mouse Bcg and Tbc-1 genes was studied. It was shown that the F1 hybrids between highly susceptible to tuberculosis mice I/St (Tbc-1s) and the Bcgs-carrying strains were highly resistant to M. tuberculosis H37Rv infection. These results point to complementation of Bcgs and Tbc-1s genes. Analysis of survival time of the [(AKR x B10-fzy)F1 x B10-Fzy]BC1 offspring showed that the mouse chromosome 1 does not regulate resistance to H37Rv infection. No linkage of the Tbc-1s gene with chromosome 1 was revealed when using fzy gene as a marker of the chromosome 1.     

Acute stress-induced tissue injury in mice: differences between emotional and social stress

Emotional stress affects cellular integrity in many tissues including the heart. Much less is known about the effects of social stress. We studied the effect of emotional (immobilization with or without cold exposure) or social (intermale confrontation) stress in mice. Tissue injury was measured by means of the release of enzyme activities to blood plasma: lactate dehydrogenase (LDH), creatine kinase (CK), aspartate transaminase (AST), and alanine transaminase (ALT). Tape-immobilization increased all these activities in the plasma. AST-ALT ratio was also increased in these animals. Electrophoretic analysis of CK isoenzymes showed the appearance of CK-MB. These results indicate that the heart was injured in immobilized mice. Analysis of LDH isoenzymes and measurement of alpha-hydroxybutyrate dehydrogenase (HBDH) activity suggests that other tissues, in addition to the heart, contribute to the increase in plasma LDH activity. Restraint in small cylinders increased plasma LDH, CK, AST, and ALT activities, but to lower levels than in tape immobilization. Because the decrease in liver glycogen and the increase in plasma epidermal growth factor (EGF) were also smaller in restraint than in the tape-immobilization model of emotional stress, we conclude that the former is a less intense stressor than the latter. Cold exposure during the restraint period altered the early responses to stress (it enhanced liver glycogen decrease, but abolished the increase in plasma EGF concentration). Cold exposure during restraint enhanced heart injury, as revealed by the greater increase in CK and AST activities. Intermale confrontation progressively decreased liver glycogen content. Plasma EGF concentration increased (to near 100 nM from a resting value of 0.1 nM) until 60 minutes, and decreased thereafter. Confrontation also affected cellular integrity in some tissues, as indicated by the rise in plasma LDH activity. However, in this type of stress, the heart appeared to be specifically protected because there was no increase in plasma CK activity, and both AST and ALT increased, but the AST-ALT ratio remained constant. Habituation to restraint (1 h/d, 4 days) made mice resistant to restraint-induced tissue injury as indicated by the lack of an increase in plasma LDH, CK, AST, or ALT activities. Similar general protection against homotypic stress-induced injury was observed in mice habituated to intermale confrontation.     

Dynamics of the interaction of hypothalamic, reticular and limbic structures and the neocortex as affected by corticosteroids

The neurophysiological analysis of the hypothalamo-reticulo-lambic structures and neocortex and dynamics of their relationship simultaneously with the content determination of the corticosteroids in rats and rabbits blood under the influence of hydrocortisone and 11-deoxycorticosterone has been carried out. It has been shown that the hypothalamo-reticulo-limbic system are involved under the action of adrenal hormones. Under the influence of corticosteroids the dynamics of changes of these structures ensuring the functions of hypophysal-adrenal complex are condition to transfer the neuroendocrine system into the new state forming definite behavioral reactions to support homeostasis.     

Correlations of central nervous system and thyroid function under chronic emotional stress

Experiments on cats exposed to chronic emotional stress induced during one week by 4-hour immobilization of the animals in conjunction with aperiodic electrocutaneous stimulation were made to study correlations of the time course of changes in the EEG of the cortical and subcortical structures and the content of thyroxin in the peripheral blood at varying time of the experiments. It was demonstrated that in the course of stress, the EEG manifests the cycles of "burst" activity of slow waves, which are first recorded in the posterior hypothalamus and then get generalized. This is accompanied by a significantly high thyroxin secretion. As the stress exposures are repeated, the EEG changes become dominant, also corresponding with high thyroxin secretion. After the experiments are over, the cycles of "burst" activity accompanied by enhanced thyroid function are still recordable over several days.