Differential Response of Central Dopaminergic System in Acute and Chronic Unpredictable Stress Models in Rats

We aimed to evaluate the response of dopaminergic system in acute stress (AS) and chronic unpredictable stress (CUS) by measuring dopamine (DA) levels, its receptor densities in the frontal cortex, striatum, hippocampus, amygdala and orbito-frontal cortex regions of rat brain, and investigated the corresponding behavioral locomotor changes. Involvement of D₁ receptor was also examined during AS and CUS using A 68930, a D₁ selective agonist. Rats were exposed to AS (single immobilization for 150 min) and CUS (two different stressors for 7 days). AS significantly decreased the DA levels in the striatum and hippocampus, and A 68930 pretreatment significantly reverted these changes. However, in the frontal cortex significantly increased DA levels were remain unchanged following A 68930. CUS led to a decrease of DA levels in the frontal cortex, striatum and hippocampus, which were normalized by A 68930. Saturation radioligand binding assays revealed a significant decrease in the number of D₁-like receptors in the frontal cortex during CUS, which were further decreased by A 68930 pretreatment. However, in the striatum and hippocampus, A 68930 pretreatment reduced the CUS induced increase in the number of D₁-like receptors. No significant changes were observed in the amygdala and orbito-frontal cortex during AS and CUS, while D₂-like receptors were unchanged in all the brain regions studied. Locomotor activity was significantly decreased in both the stress models, A 68930 pretreatment significantly increased stereotypic counts and horizontal activity. Thus, present investigation provide insights into the differential regional response of dopaminergic system during AS and CUS. Further, neurochemical and behavioral effects of D₁ agonist pretreatment suggest specific modulatory role of D₁ receptor under such stressful episodes.     

The spectral characteristics of the electrical activity in the rabbit brain during the hunger dominant]

By means of daily alimentary deprivation the dominant of hunger was created in rabbits. In response to acoustic stimuli summational swallowing and chewing movements appeared. Spectral analysis of the electrical brain activity showed the presence of primary dominant focus zone (lateral and ventromedial hypothalamus), characterized by an increase of spectrum power in delta-range while in the orbito-frontal, sensorimotor, parietal cerebral cortex, in the medial and lateral preoptic hypothalamic zones the power of biopotentials spectrum decreased within the whole analyzed frequency range.     

Increased muscarinic cholinergic receptors in prefrontal cortices of medicated schizophrenics

Alterations in 3H-quinuclidinyl benzilate binding sites associated with muscarinic cholinergic receptors were investigated in orbito-frontal and medial frontal cortices from 12 schizophrenics, 6 on-drug and 6 off-drug cases, and from 10 controls. Significantly lower affinities of the sites were found in both areas of schizophrenics than controls. An increase in receptor number was shown only in the orbito-frontal cortex from schizophrenics. On-drug group of schizophrenics did, however, show a significant increase in receptor number and a significant decrease in affinity in both areas, while there were no significant differences in any binding parameters of off-drug schizophrenics from controls. Also in the caudate the similar results were obtained. It is, thus, concluded that alterations in muscarinic cholinergic receptors of schizophrenic patients result from long-term medication with antimuscarinic actions.     

Electrophysiological analysis of corticopontine connections

In acute experiments on cats anesthetized with pentobarbital and chloralose, the method of recording focal responses was used to study projections of various parts of the orbito-frontal and basal temporal cortex and also of the hippocampus in the region of the pons. Different formations of the fronto-basal zones of the neocortex were shown to have local projections in the rostral zones of the pons and relatively diffuse projections in its caudal zones. Projections of the hippocampus in structures of the pons are less well marked than those of the fronto-basal zones of the neocortex and their focal responses are more diffuse in character. Representation of all the structures studied is found only in the nuclei of the gray matter of the pons. The orbito-insular zone of the orbito-frontal cortex is not represented in the caudal zones of the reticular formation; the basal temporal cortex has no projection in the middle cerebellar peduncles.A. M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 347–354, July–August, 1977.     

The neural correlates of desire

In an event-related fMRI study, we scanned eighteen normal human subjects while they viewed three categories of pictures (events, objects and persons) which they classified according to desirability (desirable, indifferent or undesirable). Each category produced activity in a distinct part of the visual brain, thus reflecting its functional specialization. We used conjunction analysis to learn whether there is a brain area which is always active when a desirable picture is viewed, regardless of the category to which it belongs. The conjunction analysis of the contrast desirable > undesirable revealed activity in the superior orbito-frontal cortex. This activity bore a positive linear relationship to the declared level of desirability. The conjunction analysis of desirable > indifferent revealed activity in the mid-cingulate cortex and in the anterior cingulate cortex. In the former, activity was greater for desirable and undesirable stimuli than for stimuli classed as indifferent. Other conjunction analyses produced no significant effects. These results show that categorizing any stimulus according to its desirability activates three different brain areas: the superior orbito-frontal, the mid-cingulate, and the anterior cingulate cortices.     

The encoding of temporally irregular and regular visual patterns in the human brain

In the work reported here, we set out to study the neural systems that detect predictable temporal patterns and departures from them. We used functional magnetic resonance imaging (fMRI) to locate activity in the brains of subjects when they viewed temporally regular and irregular patterns produced by letters, numbers, colors and luminance. Activity induced by irregular sequences was located within dorsolateral prefrontal cortex, including an area that was responsive to irregular patterns regardless of the type of visual stimuli producing them. Conversely, temporally regular arrangements resulted in activity in the right frontal lobe (medial frontal gyrus), in the left orbito-frontal cortex and in the left pallidum. The results show that there is an abstractive system in the brain for detecting temporal irregularity, regardless of the source producing it.     

Effects of the removal of the orbito-frontal cortex on the development of reflex analgesia

The authors studied the effect of electric acupuncture stimulation (EAP) on the changes in pain thresholds prior to and after removal of the orbito-frontal cortex (OFC) of the brain in behavioral experiments on adult cats. Removal of OFC increased the thresholds of pain response at the 4th and the 5th levels of the conventional scale, reflecting emotionally-affective manifestations of pain, and intensified the effect of antinociceptive EAP. The results obtained are analysed in relation to the inhibitory tonic effect of OFC on antinociceptive structures of the brain. Different effects of OFC and somatosensory cortex on the antinociceptive structures of the brain are discussed.     

Mechanisms of transmission of excitation grnerated in the orbito-frontal cortex]

Experiments carried out on cats showed that interhemispheric generalization of strychnine spasmodic potentials from the orbito-frontal cortex were mainly brought about by the callosal pathway. In contrast to other projection and association zones of the cortex only the frontal portion of the corpus callosum (the rostrum) and not the whole corpus took part in transmitting strychnine commissures. The results of investigations carried out were consistent with the general conception of the principle of the determining dispatch station (DDS) in the nervous system integration activity. These results reveal that the appearance of the DDS induces secondary excitation foci which fully reproduce tha work regimen of the DDS. Switching of such "mirror" foci representing "the destination stations" from the DDS influence led to the elimination of the activity induced in them.     

Chronological observations of primary somatosensory cortical maps in kittens following low thoracic (T12) spinal cord transection at 2 weeks of age.

The present study investigated the reorganization of the somatosensory cortex in kittens following T12 spinal cord transection at 2 weeks of age. Multiunit electrophysiological methods were used to map the somatosensory cortex of kittens at 3, 6, and 9 weeks after the transection. The entire reorganized cortical region was driven by substitute cutaneous inputs, primarily from the trunk, at 3 weeks after spinal cord transection. Although the level of cortical responsiveness remained the same throughout the 9 weeks studied, internal trunk representation changed, and there was an increase in shoulder girdle representation and emergence of forelimb representation. Poor somatotopic and topographic order was observed in the reorganized cortex, regardless of time posttransection. Finally, trunk receptive fields displayed a wide variety of shapes, sizes, and orientations not seen in the normal cortex.     

Gangliosides in the human brain development and aging.

In this study, brain gangliosides in prenatal and postnatal human life were analyzed. Immunohistochemically, the presence of "c"-pathway of gangliosides (GQ1c) in embryonic brain was only recorded at 5 weeks of gestation. Biochemical results indicated a twofold increase in human cortex ganglioside concentration between 16 and 22 weeks of gestation. The increasing ganglioside concentration was based on an increasing GD1a ganglioside fraction in all regions analyzed except cerebellar cortex, which was characterized by increasing GT1b. In this developmental period, GD3 was found to be localized in the ventricular zone of the cortical wall. After birth, GD1b ganglioside in neuropil of granular cell layer corresponding to growing mossy fibers was expressed in cerebellar cortex. Between birth and 20/30 years of age, a cerebral neocortical difference of ganglioside composition was observed, characterized by lowest GD1a in visual cortex. Analyzing the composition of gangliosides in cortical regions during aging, they were observed to follow region-specific alterations. In frontal cortex, there was a greater decrease in GD1a and GM1 than in GT1b and GD1b, but in occipital (visual) cortex there was no change in individual gangliosides. In hippocampus, GD1a moderately decreased, whereas other fractions were stable. In cerebellar cortex, GD1b and GT1b fractions decreased with aging.     

Chronological Observations of Primary Somatosensory Cortical Maps in Kittens following Low Thoracic (T12) Spinal Cord Transection at 2 Weeks of Age

The present study investigated the reorganization of the somatosensory cortex in kittens following T₁₂ spinal cord transection at 2 weeks of age. Multiunit electrophysiological methods were used to map the somatosensory cortex of kittens at 3, 6, and 9 weeks after the transection. The entire reorganized cortical region was driven by substitute cutaneous inputs, primarily from the trunk, at 3 weeks after spinal cord transection. Although the level of cortical responsiveness remained the same throughout the 9 weeks studied, internal trunk representation changed, and there was an increase in shoulder girdle representation and emergence of forelimb representation. Poor somatotopic and topographic order was observed in the reorganized cortex, regardless of time posttransection. Finally, trunk receptive fields displayed a wide variety of shapes, sizes, and orientations not seen in the normal cortex.     

Changes in the rate of local cerebral blood flow and cytochrome concentration in several areas of the brain of the albino rat during neurotization

In several brain parts of rats with experimental neurosis local circulation rate (LCR) was measured by hydrogen clearence method, and cytochromes content was determined by differential spectrophotometry. In early period of neurotization (up to 15 days) reciprocal LCR changes were observed in the cortex and subcortical structures, and after 18 days were reduced in all the brain parts studied. The maximum reduction was observed after three weeks of neurotization. Neurotization during one week elicited significant decrease of cytochrome a level in the cortex. Its level in the cortex after 3 weeks of neurotization and in the hypothalamus and hippocampus after one and three weeks of neurotization did not differ from its normal content. Neurotization did not influence cytochromes c + c1 levels in the structures examined.     

Nociceptive reaction-related state of glial intermediate filaments in the brain of rats with hyperfunction of the thyroid gland: An ontogenetic aspect

In experiments on Wistar rats of two age groups (5 weeks old and mature, 5 months old), we studied the content and polypeptide composition of glial fibrillary acidic protein (GFAP) in the cerebral cortex, hippocampus, thalamus, and brainstem under conditions of experimentally induced hyperfunction of the thyroid gland, as well as of combination of hyperthyroidism with the pain model (consequences of laparotomy). The hyperthyroid state was created by administration of L-thyroxine (initial dose, 10 μg/day) with food for 2 weeks; the dose was increased daily by 10 μg. At the end of experiment, we measured the level of thyroxine in the blood serum using an immunoenzymatic technique. We found that in the hyperthyroid state 5-week-old rats showed a significant increase in the content of filamentous GFAP fraction in the hippocampus, while when this influence was combined with the postoperation pain syndrome, an increase was observed in the brainstem (by 18 to 27%). Results of immunoblotting demonstrated that degraded polypeptides with a molecular mass of 47 to 45 kdalton were manifested under these conditions, which is indicative of intensification of cytoskeletal rearrangement of astroglia. In mature rats under the same conditions, we observed a drop in the level of insoluble polypeptides of intermediate filaments in astrocytes in the thalamus, hippocampus, and cerebral cortex. Neirofiziologiya/Neurophysiology, Vol. 38, No. 4, pp. 280–286, July–August, 2006.     

Unitary responses of the hypothalamic nuclei to stimulation of the frontobasal neocortex

Unitary responses in the hypothalamic nuclei to stimulation of the frontobasal zones of the cortex (proreal, orbito-insular, and basal temporal regions) were studied. Cortico-thalamic connections were found to possess definite topical organization: the orbito-frontal zones of the cortex have a more marked effect on unit activity of the hypothalamic nuclei than the basal temporal cortex. Antidromic activation, during stimulation of a particular region of the cortex, of neurons excited orthodromically by stimulation of another cortical structure, enables a number of neuronal circuits functioning within the forebrain to be distinguished. The first circuit includes the orbital gyrus, preoptic zone, and proreal gyrus. The second circuit has the same cortical components as the first, but its relay in the hypothalamus takes place in the region of the mamillary bodies. The third circuit is represented by the basal temporal cortex, lateral hypothalamus, and prefrontal cortex.M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 44–53, January–February, 1978.     

Electrophysiological analysis of the functional organization of cortico-cerebellar connections

The effect of stimulation of cortical association (orbito-frontal, parietal) and projection (auditory, sensomotor) areas on the activity of Purkinje neurons of the cerebellar cortex was studied in adult cats anesthetized with pentobarbital, with or without chloralose. These responses were compared with those to peripheral stimuli. Definite similarity was found between the responses of Purkinje cells to different cortical (association and projection) stimuli as regards both the types of responses of the neurons and their ability to respond. No similarity was observed in the responses of Purkinje cells to peripheral (visual, auditory, electrodermal) stimulation. Whereas almost identical numbers of neurons (over 50%) were excited in response to the different forms of cortical stimulation, the ability of the neurons to respond to peripheral stimuli differed considerably: 44.6% of neurons responded to electrodermal stimulation, 34.2% to auditory, and 18.8% to visual.Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 483–489, September–October, 1976.     

Effect of Motor and Premotor Cortex Ablation on Concentrations of Amino Acids, Monoamines, and Acetylcholine and on the Ultrastructure in Rat Striatum. A Confirmation of Glutamate as the Specific Cortico-Striatal Transmitter

At 1, 2, and 4 weeks after unilateral premotor and motor cortex ablation in rats, a significant and lasting decrease in glutamate levels in the ipsilateral versus contralateral striatum was observed. A significant corresponding fall in aspartate was seen only after 1 week. In contrast, there was a large increase in the striatal concentrations of lysine, threonine, alanine, and glutamine 1 week after the cortical ablation. This correlates with the extensive glial proliferation in the deafferented ipsilateral striatum. Four weeks after cortical ablation the GABA concentration was significantly increased. There was no decrease in other putative transmitters (dopamine, serotonin, acetylcholine, glycine and taurine), nor was a glutamate decrease observed in the hippocampus or in the hypothalamus, which do not receive direct premotor and motor cortical inputs. Both biochemical and morphological evidence for a minor contralateral cortico-striatal projection was obtained. Correlating with the fall in glutamate, ultrastructural observations indicated the degeneration of two types of striatal synapses, i.e., those of the axo-spinous type III and of the axo-dendritic type VII. Frontal cortex ablation clearly affects, in opposite directions, the metabolism of various striatal amino acids but not that of acetylcholine and the monoamine transmitters. The results strongly support the view that glutamate is the transmitter of the cortico-striatal fibers.     

Effect of vanadate administration on polyol pathway in diabetic rat kidney.

Effect of oral administration of sodium orthovanadate for three weeks on polyol pathway in renal cortex and medulla was studied in control and alloxan diabetic rats. An enhancement in aldose reductase in cortex and medulla and sorbitol dehydrogenase in cortex was observed in alloxan diabetic rats. Despite depressed insulin secretion, vanadate treatment to diabetic rats counteracted hyperglycemia, normalized elevated enzyme activities and glucose level, prevented medullary sorbitol accumulation and markedly checked increase in kidney weight. These results show that vanadate causes marked improvement in renal hypertrophy and has an antidiabetogenic effect on polyol pathway in diabetic kidney.     

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.     

Discovery of the sources of some descending forebrain systems by the retrograde axonal transport of horseradish peroxidase method

The location of neurons forming fiber systems descending into the brain-stem reticular formation, red nucleus, and relay nuclei of the dorsal columns was studied in cats by the retrograde axonal transport of horseradish peroxidase method. The cortical projection regions, structures of the limbic system, and the hypothalamus were shown to form fiber systems that descend to the brain stem, whereas the orbito-frontal cortex is the chief source of cortico-reticular projections. The possible functional role of these descending systems in the central control of somatic and visceral functions is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 3, pp. 218–226, May–June, 1979.     

Activation of brain structures by fMRI data when viewing the video clips and recall of shown actions

In 10 healthy volunteers, brain tomograms were recorded using an fMRI scanner with a 3T-field magnet. Emotionally neutral and emotionally involving videos were used for stimulation. Registration consisted of seven series: two series of viewing a fixation point and two kinds of video clips, one series of viewing of a succession of two types of video clips, two series of watching videos with subsequent recall, and two series of viewing the fixation point followed by recall of content online. Viewing content online caused the greatest degree of metabolism increase localized in the visual cortex. This activation was more pronounced during the presentation of an emotionally involving video clip. In addition to the occipital lobe, it actively involved the temporal, parietal and, to a lesser extent, the frontal cortex. Activation of the motor cortex was detected only in some subjects. The "interference" effect in which the increase in metabolism was minimal was observed during a consequent demonstration of video-clips. Immediate recall of video-clips after viewing caused the greatest activation of the posterior frontal and motor cortex. Delayed recall activated mostly the anterior frontal cortex. There was a decrease of metabolism in the visual cortex during the recall. The greatest reduction in the visual cortex was observed during immediate recall. Immediate and delayed recall activated the structures associated with the maintenance of consciousness, memory and a system of mirror neurons.