The effect of diethyl- -fluoroglutarate on phosphates and glutamate in slices of rabbit cerebral cortex

Abstract— The diethyl ester of α-fluoroglutarate (DEFG), an inhibitor of glutamate dehydrogenase, was prepared, and its effect on glutamate and phosphates in slices of rabbit cerebral cortex was examined. The primary effect of the drug on cortical slices incubating in a Krebs-Ringer glucose medium was to decrease the tissue levels of glutamate in association with decreased levels and turnover of high-energy phosphates. Assimilation of exogenous glutamate by the slices was partially blocked in the presence of the drug and severely depressed oxidative phosphorylation resulted when glutamate and DEFG were both present in the incubation mixture. The results suggested a significant relationship between the activity of cerebral glutamate dehydrogenase and oxidative phosphorylation. During incubation in a Krebs-Ringer glucose medium the endogenous pool of free amino acids in the cortical slice partitioned with the medium. Little or no glutamate, aspartate or GABA was present in the medium after incubation, but glycine, alanine, threonine, serine and glutamine did partition to varying degrees, with over one-half of the glutamine present in the incubation medium. With the exception of ‘leakage’ of aspartate, the partitioning patterns were relatively unaffected by the presence of added glutamate or DEFG.     

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.     

Dynamics of the direction of static connections in the electrical activity of the cerebral cortex in the cat

Data have been obtained on three cats for analysis of statistic connections of electrical activity in the visual, parietal and somatosensory cortical zones during development of evoked potentials to photic signal in these areas, and also in periods previous to photic stimulation and on traces of its action. An increase in shown of the influence of activity in the visual area on that of the somatosensory zone in post-stimulus periods and a sharp increase of two-way connections between these areas against the background of a relative equilibrium of direct and backward connections in trace periods.     

Effect of serotonin on the electrical activity of the cerebral cortex in the rabbit

Application of serotonin on the rabbit cerebral cortex produced prolonged (minutes) periodical oscillations of the activation level and the level of spatial synchronization of neocortical biopotentials. Periodical changes of biopotentials correlation were due above all to a significant reorganization of phasic correlation of the EEG theta-components of remote neocortex points. The changes may be explained by the appearance, due to serotonin, of slow oscillations of the excitation level of the cortical neurones, as a systemic transitional reaction to the change in the balance of excitatory and inhibitory processes. The ability of serotonin to influence phasic relationships of the distantly-synchronous cortical theta-rhythm is of considerable significance for conditioned activity.     

Spontaneous electrical activity of the rat cerebral cortex during microwave irradiation

A study was made of changes in spontaneous electrical activity of rat brain cortex induced by a single exposure to microwave radiation (electromagnetic fields of 0.1, 1.0, 10, and 35 mW/cm2). The animals were exposed in anechoic chambers to continuous waves at 2450 MHz in conditions of continuous generation. The data obtained indicate that the EEG parameters change under the effect of microwave radiation. The technique applied permits to study the occurrence and development of the CNS reactions to microwave radiation at the time of action of the factor.     

Effects of oxiracetam and piracetam on the electrical activity of neurons of the cerebral cortex

The effect of oxiracetam and piracetam on the spontaneous impulse neuronal activity of the somatosensory cortex of the cat and rabbit was studied. Oxiracetam and piracetam when applied microiontophoretically changed neuronal activity by depressing in the majority of the cases studied or sometimes facilitating the spontaneous firing rate. A small percentage of neurons (about 30%) remains unaffected by the application of the nootropics. In some cases oxiracetam and piracetam diminished the depress effect of morphine and DADLE on the spontaneous impulse neuronal activity.