Frontal Brain Sections Research Articles

Intercellular Contact Protein β-Catenin in Neurons of the Habenula of the Rat Brain

Studies were performed on frontal brain sections (n = 5) from Wistar rats using immunocytochemical methods. This is the first report on the detection of the protein β-catenin in the nuclei of mature neurons in the medial part of the habenula. As the intranuclear localization of this protein points to its involvement in the canonical Wnt signal pathway, which is expressed during embryogenesis, it can be suggested that habenular neurons retain properties not typical of mature neurons.

Distribution of Neuronal and Glial Antigens in Somatosensory Cortex Columns in the Rat Brain (an immunohistochemical study)

The aim of the present work was to identify columns in neocortical field S1 on frontal brain sections from white mongrel rats (n = 10) using immunocytochemical methods and antibodies to neuron proteins (synaptophysin, neurofilaments) and glial cells (glial fibrillary acidic protein (GFAP), myelin basic protein). Analysis of the expression of the main neurospecific antigens showed that on thin sections (4 μm), columns could be identified on the basis of groupings of astrocytes and neuron processes, i.e., axons and dendrites. Analysis of GFAP expression also showed that cortical layer I generally contained large numbers of large astrocytes with branching processes, as well as numerous small processes with high expression intensity. The synaptophysin content was high in all layers of the cortex, though the most intense reaction was seen in the molecular layer, as for reactions for GFAP. Expression of myelin basic protein identified radially distributed myelinated neuron processes in the cortex.

Morpho-Functional Characteristics of Hypothalamic Orexin Neurons During Experimental Autoimmune Encephalomyelitis

Background/Aim: There is growing interest in the possible role of orexin in pathophysiological processes of multiple sclerosis (MS) for these patients frequently complain of fatigue and sleep disturbances and orexin is a neuropeptide known to play the crucial role in sleep/wakefulness regulation as well as in many other physiological functions. The present study was aimed to investigate morpho-functional characteristics of hypothalamic orexin system during adoptive transfer experimental autoimmune encephalomyelitis (atEAE). Method: Immunohistochemical detection of orexin-containing neurons was carried out on frontal brain sections of intact and atEAE Lewis rats. Quantity and relative transmission density (RTD) of orexin-positive neurons were assessed in definite hypothalamic structures on different brain levels (Swanson’s atlas). Preproorexin gene expression in hypothalamic cells was

Localization of CART-Positive Neurons in the Amygdaloid Body and the Relationship between Their Immunoreactivity and the Sex Steroid Level

This is the first study reporting the locations of neurons expressing CART peptide (cocaine-amphetamine-regulated transcript) throughout all the nuclear and paleocortical formations of the amygdaloid body (AB) and demonstrating the effects of sex steroids on immunoreactivity. The immunocytochemical reaction was performed on frontal brain sections from adult rats (seven females in estrus, seven females in metestrus, and seven males). The proportions of immunoreactive neurons to the total number of neurons in adjacent sections stained by the Nissl method were assessed in estrus and metestrus. In the dorsomedial and posterior cortical nuclei and the lateral capsular subnucleus of the central field, the relative numbers of immunoreactive neurons at estrus were significantly greater than at metestrus. These results provide evidence of the involvement of the olfactory and integrative centers of the AB in the pathogenesis of drug dependence and show that new and efficient methods of gene therapy might be developed using the intranasal route for drug administration.

Changes in Cell Proliferation in the Subventricular Zone of the Brain in Adult Rats Given β-Amyloid Peptide (25–35)

The effects of intracerebroventricular administration of fragment (25-35) of beta-amyloid peptide [Abeta(25-35)] on cell proliferation in the subventricular zone of the dentate gyrus of the hippocampus in adult rats were analyzed. Animals received doses of 15 nmol of pre-aggregated Abeta(25-35) or the Abeta(35-25) control peptide, or solvent (sterile water) into the lateral ventricles. On post-injection days 1-5, rats received intraperitoneal injections of the thymidine analog 5-bromo-2'-deoxyuridine (BrdU). BrdU incorporated into DNA was detected immunohistochemically on frontal brain sections six and 12 days after peptide administration. At six days, the numbers of BrdU-containing cells in the subventricular zone showed no differences between the study groups. At 12 days, the total number of BrdU-positive cells decreased significantly in all study groups. At the same time, the number of labeled cells in rats given Abeta(25-35) was significantly greater in this brain zone than in animals given water or the control peptide. Thus, Abeta(25-35) significantly increased cell proliferation in the subventricular zone after intracerebroventricular administration.

53BP1 represses mitotic catastrophe in syncytia elicited by the HIV-1 envelope

p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe.

The Paleoamygdala: Cytoarchitectonics, Organization, and the Cytological Characteristics of Its Neurons

The aim of the present work was to compare the cytoarchitectonics, neuronal organization, and cytological characteristics of the dorsomedial, posterior medial, and posterior cortical nuclei of the amygdaloid body (AB) of the rat brain. Series of frontal brain sections stained with cresyl violet and silver nitrate impregnation by the Golgi method were studied. The results showed that rearrangements of the nuclear principle of organization of the gray matter of the nervous system into the screened organization occur within the territory of this complex of nuclei; it consists of a sparsely branched neuron system and contains neuroendocrine cells. It is concluded that this complex of nuclei is unique in terms of its structural organization and the mechanism of development of this part of the AB, which forms in the earliest stages of AB development; it is termed the "paleoamygdala."

Single Cortical Column in Area 17: The Distribution of Intrinsic Connections

Intrinsic connections are one category of neuronal cortical connections, referring to axons that remain within the same cortical area and do not travel in the white matter. Our knowledge about these connections is based on extrapolations of results on the labelling of cells in different cortical layers, but there is no direct information about the complete connectivity of a single cortical column. To study how the population of cells sending axons to the same cortical column is distributed over the cortex we microiontophoretically injected horseradish peroxidase in single cortical columns of area 17 in cat. 3-D reconstruction of the region of labelled cells was performed by using serial frontal brain sections. It was shown that afferents from layer IV cells are short range (up to 0.5 mm) and from the supragranular (II, III) and the infragranular (V, VI) layer cells are long range (up to 5 mm). The regions with labelled cells in the supragranular and infragranular layers sending axons to the very same cortical column lie in register. For columns representing the central visual field, the distribution of labelling (in a tangential plane) is elongated in the mediolateral direction, and for peripheral columns there was a tendency towards elongation in the mediolateral and rostrocaudal directions. Moreover, the majority of labelled cells were located in regions representing peripheral parts of the visual field relative to the injection site. The described connections may represent the substrate for global linking tasks and underlie several psychophysical phenomena, such as meridional and peripheral effects.

Correlation between oxytocin neuronal sensitivity and oxytocin-binding sites in the amygdala of the rat: electrophysiological and histoautoradiographic study

Central nucleus (Ce), basomedial and medial nuclei of the amygdala (AMG), and some parts of the striato-pallidal system, present high densities of oxytocin (OT)-binding sites. In order to examine whether these OT-binding sites are functional receptors, the OT neuronal sensitivity and the presence of OT-binding sites were investigated using electrophysiological and autoradiographical techniques. To identify the AMG cells, electrical stimulation of the oval subnucleus of the bed nucleus of the stria terminalis (Ov) and of the parabrachial nucleus (Pb) were performed. Somatic and auditory sensory stimulations were also tested. OT was applied by iontophoresis during extracellular single unit recordings of cells which were localized in frontal brain sections subsequently used for histoautoradiographic detection of OT-binding sites. Cells responding to Ov nucleus stimulation were located in the AMG, mainly in the Ce nucleus, whereas those responding to Pb nucleus stimulation were distributed in the Ce nucleus and in the postero lateral part of the caudate putamen. Iontophoretic OT application excited 45% of the recorded cells (43/96) among which OT alone activated spontaneous firing rate of 30 and potentiated the l-Glutamate (GLU)-induced activation on 13. These OT-sensitive neurons were located mainly in the AMG and caudate putamen areas containing OT-binding sites. These results strongly suggest that OT-binding sites found in the AMG are functional receptors upon which OT could act as a neurotransmitter and as a neuromodulator to regulate autonomic functions.

Comparison of the effects of ioversol and other contrast media on the blood-brain barrier.

Little information is available concerning the neurotoxicity of ioversol injected in animals. The effects of ioversol and other contrast media as well as vehicle control on the blood-brain barrier (BBB) were examined by injection into the left carotid artery of Mongolian gerbils 1 min prior to the i.v. injection of [8-14C]dopamine. The animals were sacrificed 1 min after the i.v. injection to prepare the frontal brain sections following the stereotaxic atlas. No uptake of the labeled substance was observed when the vehicle control and ioversol were used, suggesting that exposure to ioversol does not damage the BBB. Both meglumine sodium amidotrizoate and iohexol caused damage to the BBB, as shown in the cerebral cortex, brain stem, and hippocampus sections in the left semisphere. Iopaidol induced a much less but significant effect. Our results suggest that ioversol is an useful contrast medium.

Effects of iontophoretically applied monoamines on somatosensory cortical neurons of unanesthetized rats

The response of somatosensory cortical neurons to iontophoretic applications of monoamines was studied in unanesthetized rats. The animal's head was held in a stereotaxic apparatus by means of a painless head-restraining system implanted 8 days prior to the recording sessions. The electrodes consisted of a recording micropipette attached to a multibarreled iontophoresis micropipette. The electrode penetrations were reconstructed on camera lucida drawings of frontal brain sections. The percentage of cortical neurons responding to application of monoamines were 76% after noradrenaline, 58% after dopamine and 66% after serotonin. The differences observed among percentages of responses seemingly correlate with the relative abundance of terminal axons and receptors for each of the three monoamines in the somatosensory cortex. The vast majority of the responding neurons were inhibited by monoamines and this inhibitory effect was independent of the level of spontaneous activity. The depressant effect of the monoamines on glutamate and acetylcholine-evoked responses supports a modulatory role for these substances. Serotonin was the most potent, followed by noradrenaline and dopamine. The present study shows that when the influence of anesthesia is eliminated, the predominant effect of monoamines on cortical first somatosensory neurons is one of inhibition. These findings contrast with results obtained under some anesthetic conditions, as well as under in vitro conditions.

Effects of acetylcholine on single cortical somatosensory neurons in the unanesthetized rat

Experiments have been performed on unanesthetized rats using a chronic restraint system. The animal's head was held in a stereotaxic apparatus by means of two metallic tubes fixed on the skull with dental cement. Electrodes consisted of a recording micropipette (filled with 1 M NaCl and 2% Pontamine Blue) attached to a multibarreled micropipette for iontophoresis. Electrode penetrations were reconstructed on camera lucida drawings of frontal brain sections. The overall percentage of spontaneously active somatosensory neurons was 77% with a mean spontaneous activity of 5.9 impulse/s ( n = 405). Yet differences were observed in the proportions of active cells as well as in the mean spontaneous activity between cortical layers (both parameters being significantly higher in layers V and VI). Comparison with results obtained under urethane anesthesia [Dykes R.W. and Lamour Y. (1988) J. Neurophysiol. 60, 703–724] shows that the percentage of the spontaneously active neurons and the mean spontaneous activity were both significantly higher in unanesthetized rats (77 vs 36%; 5.9 vs 2.6 impulse/s). Nevertheless, the laminar distribution of the most active cells was similar under both conditions. In the present study, 52.3% of the neurons ( n = 380) were excited by acetylcholine and 46% ( n = 198) by carbachol. Significantly larger percentages of neurons excited by acetylcholine were found in layers Vb and VIb. These effects of cholinergic agonists—observed for the first time in unanesthetized rats—differed significantly from those previously obtained under anesthesia (33 and 34% of neurons excited by acetylcholine and carbachol, respectively) [Lamour Y. et al. (1982) Neuroscience 7, 1483–1494]. In the absence of anesthesia, cholinoceptive neurons were significantly more numerous in layers II–III. However, under both conditions, the highest percentages of excitatory responses were observed in layers Vb and VIb. A strong relation between the level of spontaneous unitary activity and the probability of being excited by acetylcholine was observed.

Quantitative analysis of neuronal mosaic formation in the mouse neocortex and hippocampus

The mosaic pattern of neurogenesis, reflected in the arrangement of concentrations of neurons intensely labeled with 3H-thymidine, was described as a result of the writers' investigations with injection of 3H-thymidine into mice at different times of embryogenesis, followed by analysis of the arrangement of the labeled cells in the neocortex and hippocampus of day-old mice [4, 5, 13]. It was concluded that the mosaic pattern of neurogenesis is determined by the nonsynchronized course of differentiation of cell groups in the ventricular zone of the embryonic brain, i.e., evidence was obtained of its discrete organization in the form of loci of neurogenesis. The aim of the present investigation was to obtain mathematical confirmation of the nonrandomness of mosaic formation of neuronal groups in the cerebral cortex, to characterize this process quantitatively, and to compare its scale with the formation of the modular organization of the cortex. EXPERIMENTAL METHOD Pregnant female CBA mice were given a single intraperitoneal injection of 3H-thymidine (i0 ~Ci/g) on the 13th-19th day of pregnancy (EI3-EI9). At the age of i day, two or three mice from each mother were killed by decapitation. The cerebral hemispheres of mice receiving 3H-thymidine from El5 to El9 were fixed in Karnovsky's fixative and embedded in Durcupan. When the isotope was injected during the period E13-19 the cerebral hemispheres were fixed in Carnoy's mixture and embedded in paraffin wax. One hemisphere from each animal was cut into frontal sections, the other into sagittal. Preparations with glued semithin (i u) or paraffin (6 B) sections were covered with type M emulsion and, after standard autoradiographic processing, were stained with 1% toluidine blue solution in 2.5% sodium carbonate solution or with 0.1% cresyl violet. The arrangement of the centers of the nuclei of the intensely labeled neurons in area 6 of the frontal region of the neocortex and in area CAI of the dorsal hippocampus was mapped on an NU-2E microscope with projection screen. Mapping in the neocortex was carried out on frontal semithin brain sections from mice receiving 3H-thymidine from El5 through EfT, whereas mapping in the hippocampus was carried out on paraffin and semithin frontal brain sections from animals receiving the isotope from El3 through El7. Cells were recorded as intensely labeled if the number of grains of silver above the nucleus varied from maximal to half that number of grains per section. Maps of areas 6 and CAI from two animals at each time of the experiment studied were analyzed mathematically to discover nonrandom groups of intensely labeled neurons. For this purpose an approach was used which enables the regularity of neurogenesis to be assessed in brain structures organized on the principle of a rec

Intra-amygdaloid injections of kainic acid: Regional metabolic changes and their relation to the pathological alterations

Kainic acid was injected unilaterally in the amygdala of the rat. Following various delays, 2-deoxy- d-[ 14C]glucose was given intravenously. Autoradiographs of frontal brain sections showed increased glucose uptake in a number of cerebral structures as compared with controls. Most of these structures belong to, or are closely related to, what is traditionally called the ‘limbic system’. The structures that show an increased glucose consumption subsequent to kainic acid injections are, with few exceptions, identical to those that are sensitive to the toxic effect that kainic acid exerts on structures distant to the site of injection. The findings are discussed in relation to the hypothesis that the latter effect is secondary to the epileptogenic properties of kainic acid.

Distribution of an α-bungarotoxin-binding cholinergic nicotinic receptor in rat brain

Cholinergic nicotinic receptors in rat brain were demonstrated by the use of the potent nicotinic antagonist [ 125I]α-bungarotoxin ([ 125I]α-Btx). Biochemical studies on binding of [ 125I]α-Btx to rat hippocampal homogenates revealed saturable binding sites which are protected by nicotine, d-tubocurarine and acetylcholine but not by atropine or oxotremorine. The hippocampus and hypothalamus displayed relatively high [ 125I]α-Btx specific binding whereas the cerebellum was devoid of specific binding. Other regions displayed intermediate binding levels. Analysis of the regional distribution of [ 125I]α-Btx binding by autoradiography of frontal brain sections revealed high labeling in the hippocampus, hypothalamic supraoptic, suprachiasmatic and periventricular nuclei, ventral lateral geniculate and the mesencephalic dorsal tegmental nucleus. It is suggested that the limbic forebrain and midbrain structures as well as sensory nuclei are the main nicotinic cholinoceptive structures in the brain.

Axonal transport in nigro-neostriatal neurons during morphine tolerance development and abstinence in rats.

Abstract—Axonal transport of [3H]protein in the nigro‐neostriatal pathway in rats was examined during acute and chronic morphine administration and during morphine abstinence. Two days after a microinjection of [3H]lysine into the left substantia nigra zona compacta, more than 95% of the radioactivity present in the rat forebrain was protein‐bound. Examination of frozen frontal brain sections revealed that 80–90% of the labelled protein of the injected side was located in brain areas traversed by the nigro‐neostriatal pathway. As a positive control, intranigrally administered colchicine reduced the amount of [3H]protein transported after 5 days to the nucleus caudatus‐putamen (neostriatum) to approx 18‐26% of control. In animals rendered morphine‐dependent by subcutaneous implantation of tablets containing 75 mg of morphine base, 27–86% more radioactivity accumulated in the neostriatum at 3, 4 and 5 days after [3H]lysine injection. In contrast, 23–48% less radioactivity was recovered in the neostriatal areas of animals withdrawing from morphine 24 h after [3H]lysine. Gel electrophoresis of soluble and particulate [3H]protein fractions from neostriatal tissues indicated that the gel patterns of radioactivity were not altered by chronic morphine administration. Neither morphine administration nor morphine abstinence altered the rate or amount of [3H]lysine incorporation into protein of the substantia nigra. These data demonstrate that chronic morphine administration was accompanied by a generalized increase in the amount of labelled protein transported to the neostriatum but the procedure was not sufficiently sensitive to detect a minor qualitative alteration of any particular protein(s). Furthermore, these data suggest that either the capacity or the rate of nigro‐neostriatal protein transport may be increased during chronic morphine administration in the rat.

Anatomical correlation between some cortical and subcortical brain structures

Investigation of frontal brain sections of 10 cats, 30 dogs and 20 people revealed a topographic correlation between certain cortical and subcortical structures: the beginning of fissura. Sylvii (the so-called "fossa Sylvii") and commissura alba cerebri anterior are located always in the same stereotaxic frontal plane. A method of practical application of the revealed topographic correlation is suggested for the stereotaxic operations on higher animals and human beings.