Regional features of background electrical activity and of direct cortical response by the intact or neuronally isolated cortex

Background electrical activity and thresholds for the appearance of direct cortical responses (DCR) were studied in acute and chronic experiments on cats in some gyri of the intact and neuronally isolated cortex (the whole cortex was subjected to neuronal isolation [10]). It was determined that in intact animals the suprasylvian gyrus, particularly its central part, differs by its higher electrical activity and lower DCR thresholds from the ectosylvian gyrus. These differences are retained after neuronal isolation of the cortex from the subcortical structures. Hence the differences found in the neurophysiologic characteristics of the gyri under study reflect specific properties and are not mediated by subcortical neural effects.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 52–58, January–February, 1970.     

The characteristics of cholinesterase distribution in the development of the human and mammalian brains]

Histochemical studies have been made on the distribution of acetyl- and butyrylcholinesterases (ACHE and BCHE) in various parts of the human and rat brain. Statistical analysis showed that at the 8th week, the highest ACHE activity in the human foetus is observed in the intermediate and plexiform layers of the cerebral cortex. The highest BCHE activity was found in the ependymal layer of various cerebral regions. High BCHE and ACHE activities were noted in the dorsal thalamus and epithalamus. In 10-week human foetuses, total high level of ACHE and BCHE was revealed in various nuclei of the thalamus and subcortical structures of the forebrain (Meynert nucleus, nucleus caudatum). In rats, the highest ACHE activity at the 14th day of prenatal life was found only in subcortical structures of the forebrain. Accumulation of BCHE activity in some of the thalamic nuclei of rats begins at the 10-17th day of postnatal life.     

DEVELOPMENTAL AND REGIONAL VARIATIONS IN NEUROTRANSMITTER-SENSITIVE ADENYLATE CYCLASE SYSTEMS IN CELL-FREE PREPARATIONS FROM RAT BRAIN

Investigations have been carried out on regional and developmental variations in the properties of adenylate cyclase systems in participate preparations from rat brain. EGTA was routinely included in the assay medium to minimize differences in the state of activation of these systems resulting from variations in their exposure to endogenous Ca²⁺. At birth, adenylate cyclase activity was much higher in the hindbrain-medullary preparations than in comparable fractions from cerebellum, cerebral cortex or subcortex (including midbrain, corpus striatum, hypothalamus and hippocampus). Adenylate cyclase activity increased during early development in preparations from all areas of the brain. Maximal levels were reached at 14 days of age or later. These levels were not greatly altered in the young adult animal, except in the hindbrain-medullary area, where a decrease in activity was observed. Adenylate cyclase systems in cerebral cortical and subcortical preparations were activated by norepinephrine and dopamine throughout development. Serotonin also stimulated adenylate cyclase activity in these preparations from young animals but was much less effective in comparable fractions from adult rats. The response to dopamine was diminished with age in cerebral cortical preparations, but not in subcortical fractions. The responses to norepinephrine increased in both brain regions during early development. Adenylate cyclase systems in particulate preparations from the cerebellum and hindbrain-medullary areas exhibited relatively poor responses to the biogenic amines. Detailed studies of the properties of the cerebral cortical adenylate cyclase systems revealed enhancement of activity by Ca²⁺ and F^? at all stages of development with the maximal activation at 2–3 weeks of age. The results suggest that developmental differences in hormonal sensitivity of adenylate cyclase systems from diverse areas of the brain are related to changes in the proportions of the receptor-enzyme complexes responsive to the different biogenic amines.     

Synchronization of electrical field potentials in neocortex of rat after isolation of a cortex island in the contralateral brain hemisphere

A correlation between the number of boutons and synchronization of electrical activity in two sites of the intact right somatosensory cortex of rats was anakyzed at different stages of axonal sprouting elicited by isolation of a cortex slab in the left cortex. Time delay between the development of epileptiform field potentials in two sites of intact cortex located at a distance of 4 mm from each other was determined as a parameter of synchronization. The analysis was carried out in 30 and 90 days after the complete isolation of the neural island in a symmetrical site of the contralateral cortex. Epileptiform activity was induced by penicillin. A significant increase in the number of boutons in the II and V layers of the intact cortex observed 90 days after the isolation of neural island in a symmetrical site of the cortex corresponded to a significant decrease in the delay of electrical activity development. Similar effects were observed in the V layer of the island 30 days after the isolation. The results suggest that the cortex lesion activates formation of new synaptic boutons in a contralateral site and increases a degree of synchronization of electrical activity, which may affect the epileptogenesis. The data suggest that pyramids of the III and, most probably, V layers form a neuronal network in the rat neocortex thus providing synchronization of epileptiform field potentials.     

Excess of taurine supplementation in rat: effects on GABA-related amino acids in developing nervous tissues.

The effects of taurine supplementation on GABA-related amino acid homeostasis in developing nervous tissues of suckling rats were studied. In the first two weeks of postnatal growth, cerebral cortex and cerebellum appear more accessible to taurine supplementation in comparison to retina; in addition, different changes in excitatory/inhibitory amino acids were observed. After the 5th day of life, in the retina and cerebellum of taurine-supplemented pups a decrease in GABA levels was found; in contrast, in cerebral cortex GABA content significantly increased throughout 20 days of postnatal growth. In all nervous tissues studied (except for cerebellum) glutamine concentration increased at the 5th day; then in cerebellum and in retina, but not in cerebral cortex, a significant decrease until the 20th day occurred. Furthermore, in cerebellum and retina taurine supplementation decreased glutamate levels, in comparison to controls, at the 10th and until the 20th day of postnatal life, respectively, whereas in cerebral cortex an increase in glutamate level was observed only at the 5th day. In conclusion, taurine supplementation, in excess to the usual amount from the mother's milk, affected the glutamate compartments in various cell types. The changes in GABA-related amino acid concentrations in cerebral cortex, cerebellum, and retina may depend on the different pattern of the metabolic processes at different maturative stages.     

Effects of Thyroxine on Methionine Adenosyltransferase Activity in Rat Cerebral Cortex and Cerebellum During Postnatal Development

Abstract: Methionine adenosyltransferase (MAT) activity was evaluated in cerebral cortex and cerebellum in controls and in rats treated with thyroxine. In controls the enzyme showed a different pattern in cerebral cortex and cerebellum during neonatal and late suckling periods. Hyperthyroid rats showed a significant increase of the enzyme in cerebral cortex only at the 2nd day of the neonatal period; in cerebellum the developmental pattern of MAT in neonatal period was anticipated temporally by 2–4 days. During the late suckling period thyroxine treatment produced in cerebellum a significant decrease in MAT activity at the 15th day after birth. From these data, we propose that hyperthyroidism may cause precocious induction of MAT both in cerebral cortex and in cerebellum and that the increased availability of S -adenosyll-methionine during the neonatal period could be related to its utilization also in polyamine biosynthesis.     

Is Remodelling of Corticospinal Tract Terminations Originating in the Intact Hemisphere Associated with Recovery following Transient Ischaemic Stroke in the Rat?

Following large strokes that encompass the cerebral cortex, it has been suggested that the corticospinal tract originating from the non-ischaemic hemisphere reorganises its pattern of terminal arborisation within the spinal cord to compensate for loss of function. However many strokes in humans predominantly affect subcortical structures with minimal involvement of the cerebral cortex. The aim of the present study was to determine whether remodelling of corticospinal terminals arising from the non-ischaemic hemisphere was associated with spontaneous recovery in rats with subcortical infarcts. Rats were subjected to transient middle cerebral artery occlusion or sham surgery and 28 days later, when animals exhibited functional recovery, cholera toxin b subunit was injected into the contralesional, intact forelimb motor cortex in order to anterogradely label terminals within cervical spinal cord segments. Infarcts were limited to subcortical structures and resulted in partial loss of corticospinal tract axons from the ischaemic hemisphere. Quantitative analysis revealed there was no significant difference in the numbers of terminals on the contralesional side of the spinal grey matter between ischaemic and sham rats. The results indicate that significant remodelling of the corticospinal tract from the non-ischaemic hemisphere is not associated with functional recovery in animals with subcortical infarcts.     

Hypermethioninemia Increases Cerebral Acetylcholinesterase Activity and Impairs Memory in Rats

In the present study we investigated the effect of chronic hypermethioninemia on rat performance in the Morris water maze task, as well as on acetylcholinesterase (AChE) activity in rat cerebral cortex. For chronic treatment, rats received subcutaneous injections of methionine (1.34–2.68 μmol/g of body weight), twice a day, from the 6th to the 28th day of age; control rats received the same volume of saline solution. Groups of rats were killed 3 h, 12 h or 30 days after the last injection of methionine to AChE assay and another group was left to recover until the 60th day of life to assess the effect of early methionine administration on reference and working spatial memory of rats. AChE activity was also determined after behavioral task. Results showed that chronic treatment with methionine did not alter reference memory when compared to saline-treated animals. In the working memory task, we observed a significant days effect with significant differences between control and methionine-treated animals. Chronic hypermethioninemia significantly increased AChE activity at 3 h, 12 h or 30 days after the last injection of methionine, as well as before or after behavioral test. The effect of acute hypermethioninemia on AChE was also evaluated. For acute treatment, 29-day-old rats received one single injection of methionine (2.68 μmol/g of body weight) or saline and were killed 1, 3 or 12 h later. Results showed that acute administration of methionine did not alter cerebral cortex AChE activity. Our findings suggest that chronic experimental hypermethioninemia caused cognitive dysfunction and an increase of AChE activity that might be related, at least in part, to the neurological problems presented by hypermethioninemic patients.     

The effect of ethanol exposure in pregnancy on maturation of monoaminergic systems in the developing rat bran

Simultaneous study of the main neurotransmitter of monoaminergic system of the brain, its metabolites, activity of catechol-O-methyltransferase (COMT) and the state of different subtypes of dopamine (DA) receptors in the developing brain of offspring from mothers alcoholized in gestation and feeding periods revealed a decrease in activity of all monoaminergic systems studied with reduction of noradrenaline and DA level in alcoholized fetus as well as of mPNA of COMT, an enzyme of catecholamine metabolism, in the structures of the forebrain on the 17th day but not on 13th day of prenatal development. In parallel experiments, an increase of the contents of both long and short splice variants of D2 DA receptor was registered. In postnatal period (days 4, 10, 17), further decrease of the DA system activity was observed, particularly a reduction of DOPAC level and DOPAC/DA ratio in rat litter, mothers of whom took alcohol in the gestation period with withdrawal it after birth of offspring. The serotonin system activity was also reduced in alcoholized litter in the postnatal period and was registered in the early stages (on the 4th day of life). Therefore, the serotonin system activity is changing at early stages of development (the 4th day), whereas inhibition of the DA system activity is registered at later stages (the 10th day of life).     

Changes in the electroencephalographic and gamma-aminobutyric acid transaminase and succinic semialdehyde dehydrogenase in the allergen induced rat brain

Electroencephalographic activity and gamma-Aminobutyric acid Transaminase together with Succinic semialdehyde dehydrogenase activity changes produced by sensitization with Prosopis juliflora pollen allergen were studied in the cerebral cortex and hypothalamus of the rat brain. Electrical activity of EEG recording begins to appear on 3rd day after sensitization with maximum increase in activity was found on day 9 and decreased after that. A sudden increase in electrical activity was produced in 9th day sensitized rat with 10 min after giving challenging dose intravenously. The measurement of enzymatic activity of GABA-T and SSA-DH showed decrease and increase in 3, 9, 15 and 30 days sensitized rat hypothalamus and cerebral cortex whole homogenate and mitochondrial fractions. A maximum changes in enzymatic activity was found in 9th day sensitized rat with significant alterations after giving sudden stress as challenging dose. These changes in EEG activity and GABA-ergic neurotransmitter in allergenic rats showed the immunoregulatory role of nervous system mediated via GABA shunt.     

RNA synthesis in different regions of rat brain at various time intervals after cerebellectomy

RNA synthesis was studied in cerebral cortex, thalamus and brain stem of rat, on the 3rd, 8th, 30th and 75th day after cerebellectomy. An increased RNA synthesis was detected in thalamus at the 30th day and in cerebral cortex and brain stem at the 75th day after cerebellectomy. Our findings suggest that motor compensation following the cerebellectomy could be supported by a spatio-temporal organization of macromolecular synthesis in different brain regions.     

Effect of adrenaline and triamcinolone on cytochrome oxidase activity in the brain and liver of young and adult rats.

The effect of adrenaline (0.15 i.p./kg b.w.) and of the synthetic glucocorticoid triamcinolone (40 mg i.p./kg b.w.) on cytochrome oxidase activity, the terminal enzyme of the cytochrome system, was studied in homogenates of the cerebral cortex, subcortical formations (including the basal ganglia, the thalamus and the hypothalamus), the medulla oblongata and the liver of 5-day-old and adult rats. Activity in the above mentioned homogenates was measured polarographically 15 and 30 min after administering adrenaline or 48 h after administering triamcinolone. Fifteen minutes after its injection, adrenaline caused a statistically significant drop in cytochrome oxidase activity in the cerebral cortex, subcortical formations and liver of 5-day-old rats. The decrease still persisted 30 min after administration of the hormone, but was intensified only in the liver. In adult rats, on the other hand, a significant increase in activity was observed in the cerebral cortex and liver after adrenaline. Triamcinolone had no effect on cytochrome oxidase activity in any of the given parts of the brain in either young or adult rats. It significantly stimulated cytochrome oxidase activity in the liver of 5-day-old rats, but severely inhibited it in the liver of adult rats.     

Postnatal changes in dolichol-pathway enzyme activities in cerebral cortex neurons.

Neuronal perikarya were isolated from rat cerebral cortex at different stages of postnatal development. Membranes sedimenting at 100000 g were obtained from these neurons to study several glycosyltransferases of the dolichol pathway. Enzyme activities from stages before and during synapse formation were compared (days 5 and 15 respectively). Dolichyl diphosphate (Dol-P-P) N-acetylglucosamine, dolichyl phosphate mannose and dolichyl phosphate glucose synthases and the enzymes catalysing Dol-P-P-GlcNAc2Man9Glc3 formation were higher at day 15 of postnatal development. The glycosyl transfer of the latter compound to endogenous protein(s) as well as to a dinitrophenyl-heptapeptide was also measured. The activity was higher at day 15. Furthermore, the activity of dolichyl phosphate mannose synthase was also measured during the time when the number of synapses ceased to increase (day 36) and in the adult stage. The activity of dolichyl phosphate mannose synthase was higher at day 36 than at day 15, and declined in the adult stage. From these results it may be concluded that there is an increase in the glycosylation of asparagine-type glycoproteins during synapse formation in the neurons of the cerebral cortex.     

Enhanced Brain Cell Proliferation Following Early Adrenalectomy in Rats

We have previously demonstrated an increase in adult brain DNA content in rats adrenalectomized on postnatal day 11. The present studies examined cell proliferation in cerebral cortex, cerebellum, hippocampus, and midbrain-diencephalon following adrenalectomy at this age. Compared to sham-operated controls, adrenalectomized animals showed increased [3H]thymidine incorporation into DNA (measured at 1 h following a pulse injection) in all brain regions at 7 and 14 days postsurgery. In some areas, the effect was already present as early as 2 days following adrenalectomy. Chronic replacement with corticosterone prevented this increase in DNA labelling in a dose-dependent manner. When cell proliferation in the cerebral cortex and cerebellum was independently assessed by measuring changes in thymidine kinase activity, enzyme activity was significantly elevated in both areas at 7 and 14 days postsurgery. Finally, histological examination of the cerebellar cortex suggested a delayed disappearance of the external granular layer in several cerebellar lobules of adrenalectomized animals. Overall, these findings indicate that day-11 adrenalectomy leads to a prolonged stimulation of mitotic activity in areas where cell formation at this time is exclusively glial (i.e., cerebral cortex and mid-brain-diencephalon) as well as in areas where postnatal neurogenesis is also occurring (cerebellum and hippocampus). It is hypothesized that this stimulation results from the removal of a tonic inhibitory effect exerted by circulating glucocorticoids in the normal intact animal.     

Expression of thrombospondin-1 and CD36 and CD47 receptors in the rat brain after exposure to damaging factors in the early postnatal period

The expression of thrombospondin-1 (TS-1) and its receptors CD47 and CD36 in the cerebral cortex and hippocampus of rats under damaging factors in the early postnatal period was studied. After hypoxia on the 7th day of postnatal development, an increase in the number of CD47-expressing cerebral endothelial cells (days of postnatal development: P28–P70) and reduction in the number of TS-1-expressing astrocytes in the cortex at P28 were observed. In animals subjected to early postnatal stress at the age of P2–P15, a decrease in TS-1-expressing astrocytes in the cortex and hippocampus was registered (predominantly at the age of P28). It was noted that these changes characterize the period of long-term effects (P28–P70) of early stress that is relevant to the processes of reparative angiogenesis and arresting of neurological deficits.     

Formation of alimentary conditioned reflexes with probable reinforcement in rats with frontal cortex injuries

Alimentary conditioned response to the sound of turning of the feeding-rack reinforced in 33 and 25 per cent of cases was formed faster in rats with frontal cortical lesion than in intact animals. The results obtained permit to suppose that during integrative brain activity the frontal areas of the cerebral cortex participate in organization of behavior with a high probability of reinforcement.     

DEVELOPMENTAL PROFILES OF GANGLIOSIDES IN HUMAN AND RAT BRAIN

Abstract— The developmental profiles of individual gangliosides of human brain were compared with those of rat brain. Interest was focused mainly on the pre- and early postnatal development. Human frontal lobe cortex covering the period from 10 foetal weeks to adult age and the cerebrum of rat from birth to 21 days were analysed. Lipid-NANA and lipid-P were followed; in the rat, also protein and brain weight. A limited number of samples of human cerebral white matter and cerebellar cortex were also studied. The following major results were obtained:

• 1 The ganglioside concentration increased approximately three-fold within a short period: in rat cerebrum, from birth to the 17th day; in human cerebral cortex, from the 15th foetal week to the age of about 6 months. The largest increase in the rat brain occurred by the 11th to the 13th day; in human brain by term. The relative increase of gangliosides during this period was more rapid than that of phospholipids.
• 2 A hitherto unknown distinct early period of ganglioside and phospholipid formation in rat occurred by the second to fourth day.
• 3 The changes in brain ganglioside pattern, characteristic of the developmental stages of the rat, were found to be equally pronounced in the human brain.
• 4 Regional developmental differences in the ganglioside pattern were demonstrated in human brain. A characteristic white matter pattern, rich in monosialogangliosides, had developed by the age of 1 year. The increase in ganglioside concentration and the formation of the definitive ganglioside pattern of cerebellar cortex occurred later than in cerebral cortex. This cerebellar pattern was characterized by a very large trisialoganglioside fraction.
• 5 The two periods of rapid ganglioside metabolism in rat brain preceded the two periods of rapid protein biosynthesis.

     

The effects of sleep on neurons in isolated cerebral cortex.

Slabs of cat parietal cortex with some 2 mm of underlying white matter were surgically isolated from the rest of the nervous system, without interference with the superficial blood supply. Wire micro-recording electrodes were inserted into the isolated cortex; bone, muscle and skin wounds were repaired and the animal allowed to recover from anaesthesia. The adequacy of surgical isolation was examined histologically 8--12 weeks after operation. Only one of the six preparations reported here showed surviving neural connections with the rest of the brain. Soon after operation, spontaneous bursts of neural activity appeared within the isolated area. These became more frequent until neural discharge was continuous but irregular. Our records were made from this time onwards. The interval distributions obtained from neurons within the isolated area did not differ significantly from log-normal curves. When the unrestrained animal fell asleep, there was no significant alteration in the model interval or geometric standard deviation of interval distributions recorded from cells in isolated cortex. The interval distributions of neurons in isolated cerebral cortex resembled those of neurons in the intact cortex of an alarmed animal. It is concluded that the reduction of modal interval that is shown by neurons in intact cortex when an animal falls asleep is probably due to the neural influence of infracortical structures.     

A neurophysiologic study of sleep in children during the first year of life]

Polygraphic investigation of day sleep has been carried out in thirty suckling infants (aged from 25 days to 12 months). EEG, OCG, SGR, respiration ECG, muscular activity, and in some infants, also rheographic parameters (REG and RG of the shin) have shown that already at an early nursing age, states of drowsiness, falling asleep, light and medium depth and deep slow sleep set in, as well as the so-called rapid sleep which occurs only after slow sleep. The denotation of the slow sleep stages is based on the classification by Loomis et al., though their electroenecepholographic expression in the infant is in many ways peculiar and undergoes certain dynamics during the first year of life. Peculiarities of the central area EEG have been exhibited in all the age groups, and it has been assumed that the central parts of the cortex of a suckling infant are a kind of "window" into the subcortical parts. While EEG, displaying new forms of activity at certain stages of sleep undergo distinct age changes, vegetative sleep manifestations display only some age depending quantitative differences. Thus, at the nursing age the mechanisms of electroencephalographic and vegetative sleep manifestations are of different degree of maturity: they possess a considerable autonomy, although they function in concord.