The effect of anoxia on changes in the phosphoinositide content and bioelectrical activity in the cat cerebral cortex]

The dynamic of the phosphatidylinositol (PI), the phosphatidylinositol 4-phosphate (PIP) and the phosphatidylinositol-4,5-diphosphate (PIP2) contents were studied in the correlation with the neuronal spike activity in cat brain cortex under acute oxygen deficiency caused by cessation of artificial ventilation for 1, 2.5 and 5 min. It was shown that the 1-min anoxia produced the depression of both PIP and PIP2 contents. The depression was followed by the development of the 'asphyxia neuronal activation'. During 2.5 and 5 min of anoxia the decrease of PIP2 content and increase of PIP one were detected against a background of neuronal bioelectrical activity depression. The PI content was constant during all the anoxic period.     

Ultrastructural changes in the cerebral cortex following transcranial micropolarization]

Electron microscopy of the cerebral cortex in cats and monkeys following transcranial micropolarization (TCMP) demonstrated ultrastructural changes whose degree was dependent on the electric current intensity and the stimulation period. In the focus of stimulation the current affected the brain tissue directly, different elements of the cerebral cortex showing unegual sensitivity to various TCMP regimens. The glia was the first to respond, then the neuronal bodies, and the last -- the synaptic structures. In the areas distant from the TCMP focus synaptic components altered first. The ultrastructural changes revealed were not of pathological character.     

Changes in the cerebral cortex in the progeny of DOCA-dependent females]

Methods of light microscopy and morphometrical analysis were used for studying semithin sections of the antero-parietal portions of the cortex of neonatal rats from mothers treated by desoxycorticosterone acetate (DOCA) during the last 7 (II group) of last 14 days (III group) of gestation. Animals of the III group were given greater doses of DOCA. Experimental neonatal rats had greater absolute and relative masses of the cerebrum and the thicker cortex: in the II group at the expense of enlargement of neurons, greater amount of glioblasts and the volume of neuropile; in the III group--at the expense of still greater neuron sizes, enlargement of glioblasts and their greater number, as well as the growth of the neuropile volume. In the neocortex of the II group of animals processes of proliferation of glioblasts were more pronounced, greater doses and amount of actions of DOCA (III group) being followed by processes of reinforced differentiation of nerve and glial cells. Experimental animals were found to have greater amount of microgliocytes, hypertrophy of endotheliocyte and pericyte nuclei. Symptoms of blood stagnation and perivascular edema were very rarely noted in neonatal rats of the III group.     

Dynamics of axonal degeneration in the neuronally isolated cerebral cortex]

The brains of 11 cats were studied after unilateral isolation of the cortex after M. M. Khananashvily (1961) by means of resection of the projection fibres connecting the cortex with subcortical formations. The character and peculiarities of axonal degeneration in the large hemisphere cortex, were investigated after Nauta and Fink--Heimer. It was found that distribution of degenerating terminals in every layer depended on the time when the material was taken for investigation. Maximal concentration of the degenerating fibres was observed 3--5--10 days after the operation, then a gradual decrease in density of degeneration in every cortical layer was observed. By the 9th month after the operation, the processes of axonal degeneration completely came to their end. The problem of retrograde and anterograde nature of the axonal degeneration in the cortex of the large hemispheres was discussed in the article and it was demonstrated that in the field 4 of the neuronally isolated cortex it is of mixed nature.     

Anoxia-induced changes in cAMP contents in the cat cerebral cortex]

Effect of the cessation of oxygen supply on cAMP content and neuronal spike activity (NSA) in the cortex brain was studied. The interruption of oxygen supply during in first decades of seconds evoked changes in the pattern of NSA, followed with the decrease of cAMP content (to 56 +/- 10%). Then the phase of neuronal hyperactivity and increase of cAMP level (to 198 +/- 26%) took place. The content of cAMP approximated the basal one in 2.5 min anoxia. Anoxia during 5 min resulted in direct opposite shifts of cAMP content in two groups of cats (an increase up to 223 +/- 11%, and decrease up to 75 +/- 8%, respectively, which correlated with individual features of NSA recovery in postanoxic period and values of cAMP basal level in the cortex of different animals. Upon 30 min reoxygenation after 2.5 min anoxia a decline of the content of cAMP (to 63 +/- 12%) accompanied enhance of NSA. This period of reoxygenation after 5 min anoxia demonstrated two types of reactions, observed in different groups of cats: the first type--NSA tended to normalization with the level of cAMP 44 +/- 8% below basal level, and the second type--insufficient recovery of NSA attended by value of cAMP 90 +/- 13% above basal level.     

Dynamics of the dendrite and transcallosum potentials in the cerebral cortex in overheating]

Experiments were conducted on awake rabbits placed in a thermochamber at the temperature of 45 degrees C. The dendrite and the transcallosum potentials were examined in dynamics of the hyperthermia and after the restoration of the thermal homeostasis. The influence of high temperature was accompanied by an expressed inhibition of the amplitude of the dendrite potential, although to a lesser degree than of the transcallosum response. The data obtained could testify to a direct inhibitory thermal effect on the neuron elements of various layers of the cortex. Restoration of the cortical neuron function after the high degree hyperthermia occurred twenty-four hours after the body normothermia was reached.     

Electrographic manifestations of "falling asleep" in isolated cat cortex]

Experiments were conducted on unrestricted cats; a study was made of the electrical activity of the neuronally isolated cortex during the wakeful hours and sleep. Transition from wakefulness to sleep was accompanied in the isolated cortex by the manifestations of drowsiness accompanied by the corresponding changes in the electrocorticogram of the isolated hemisphere. Electrographic manifestation of drowsiness in the isolated cortex depended on the time lapse after the operation and was mostly pronounced during the late period after the isolation of the cortex.     

The effect of electric stimulation of different regions of the cerebral cortex on the alimentary reaction in rabbits]

The influences of different parts of the neocortex on the rabbit alimentary behaviour produced by stimulation of the hypothalamic "alimentary centre" were studied in chronic experiments on rabbits with electrodes implanted in different formations of the limbic system and the midbrain. It has been found that electrical stimulation of the frontal and anterior parietal cortical areas raised the threshold of the evoked alimentary reaction. Inhibitory influences of the frontal areas proved to be stronger and more prolonged than those of the anterior parietal area. Electrical stimulation of the posterior parietal and occipital cortical areas decreased the threshold of the evoked alimentary reaction. Coagulation of the dorsal hippocampus eliminated the inhibitory influences of the neocortex, while coagulation of the mesencephalic reticular formation discontinued the facilitating influences of the neocortex on the alimentary reaction.     

Inhibitory processes in the cerebral cortex and the anticonvulsive action of benzodiazepine derivatives]

A comparative study of the effect of some benzodiazepine deprivatives (chlonazepam, lorazepam, diazepam, and medazepam) on the recovery cycles of the interzonal response was carried out on unanesthetized curare-immobilized cats. These drugs proved to selectively inhibit the testing potential within the range of 20 to 100 msec. between the conditioning and the testing stimuli. This indicates that potentiation of GABA-ergic inhibition in the cerebral cortex. The threshold doses of the drugs inducing the depression of the test response and of ED50, preventing the development of convulsions, caused by GABA deficiency or by GABA-ergic receptor block, were compared; a correlation between the mentioned effects was demonstrated. The significance of GABA-positive effect of benzodiazepines in the mechanism of their anticonvulsive activity is suggested.