GABA(A) receptor characterization and subunit localization in the human sub-ventricular zone

It is now well established that the human brain continuously produces new stem cells until well into old age. One of these stem-cell rich areas in the human brain is the sub-ventricular zone (SVZ). The human SVZ is organized in four distinctive layers containing type A, B and C cells. To date, no studies have investigated the distribution of inhibitory neurotransmitters such as γ-aminobutyric acid (GABA) and their respective receptors on the different cell types in the human SVZ. GABA(A) receptors (GABA(A)R) are ubiquitously expressed, inhibitory heteropentameric chloride ion channels comprised of a variety of subunits that are targeted by many prescribed drugs. In this study we present detailed immunohistochemical data on the regional and cellular localization of α₁, α₂, α3, β₂,₃ and γ₂ subunits of GABA(A)R in the human SVZ. The results from our double and triple labeling studies demonstrate that the cell types and subunit composition throughout the SVZ is heterogeneous; the thickness of the SVZ and GABA(A)R α₂ and γ₂ expression is increased especially in the vicinity of large SVZ blood vessels. GABA(A)R γ₂ is the most specific to the SVZ and present on various cells that express, either glial fibrillary acidic protein (GFAPδ) or polysialic acid-neural cell adhesion molecule (PSA-NCAM) separately, or together in a respective ratio of 7:6:2. Proliferating (type C) cells in the SVZ express GAD65/67, GFAPδ and GABA(A)R β₂,₃ receptor subunits. Within the SVZ the majority of cells have an unexpected nuclear GABA(A)R β₂,₃ expression that is inversely proportional to that of PCNA (proliferating cell nuclear antigen marker), which is a very different pattern of expression compared with underlying caudate nucleus cells. Taken together our results provide a detailed description of the chemo-architecture of the adult human SVZ demonstrating the importance of GABA and GABA(A) receptors on the various cell types in the SVZ.

Abnormalities of tau-protein and beta-amyloid in brain ventricle cerebrospinal fluid

OBJECTIVE

Determination of various biomarkers, such as beta-amyloid, tau-protein, phosphorylated tau-protein in CSF and their sensitivity and specificity in neurodegenerative brain processes, in particular Alzheimer Dementia (AD), has been recently investigated to monitor their abnormalities in the CSF at early stages of diseases before the clinical manifestation.

DESIGN AND SETTING

In the pilot group of our patients (10 men / 5 women) who underwent a drainage neurosurgical procedure for diagnosis of hydrocephalus, CSF was obtained from the brain ventricles and the influence of a different compartment of the CSF on the level of biomarkers, tau-protein and beta-amyloid, was investigated.

RESULTS

The mean tau-protein level for all 15 patients was 812.0 pg/ml, with median value 363.7 pg/ml; while mean beta-amyloid level for all 15 patients was 526.7 pg/ml, with median value 239.5 pg/ml, respectively. The abnormal tau-protein and beta-amyloid levels were found in the subgroup of patients in whom hydrocephalus was caused by a severe pathological process, such as brain tumor. The beta-amyloid values were significantly lower also in comparison with our previously published results in patients with AD in the CSF obtained by lumbar puncture in the spinal canal.

CONCLUSIONS

CSF in the brain ventricles is theoretically more stable and the values in this CSF probably provide more reliable informations for clinical diagnostic procedure than those for the CSF obtained by lumbar puncture in the spinal canal.

Immunohistochemical changes related to ageing in the mouse hippocampus and subventricular zone

We investigated mainly immunohistochemical changes of nestin (a marker of neuroepithelial stem cells) and Ki-67 (a marker of proliferating cells) proteins related to ageing in the mouse hippocampus and subventricular zone (SVZ) using young adult (8 weeks old) and middle-aged (40 weeks old) mice. In the present study, no significant changes in neurons and astrocytes of the hippocampal CA1 sector were found in a middle-aged male ICR mice without severe senile weakness, as compared with young adult animals. In contrast, a significant change in the number of microglia was found in the hippocampal CA1 sector of the middle-aged mice. Furthermore, no significant changes in the number of nestin- and Ki-67-positive cells were observed in the hippocampal CA1 sector of the middle-aged mice. On the other hand, decreases in the number of nestin- and Ki-67-immunopositive cells were observed in the SVZ of the middle-aged mice. Furthermore, a migration of nestin- and Ki-67-immunoreactive cells in the corpus callosum was not observed in the SVZ of the middle-aged mice. In the dentate gyrus, significant decreases in the number of Ki-67-immunopositive cells were observed in the middle-aged mice. Our study also showed that nestin immunoreactivity was observed in both Ki-67-postive cells and astrocytes in the SVZ of young adult mice. These findings emphasize the need to recognize ageing as important factors in studies of microglia, which may help to clarify the role of glial cell structure and function during ageing processes. Furthermore, the present findings suggest that ageing processes may decrease neurogenesis in the corpus callosum, SVZ and dentate gyrus. Thus our present findings provide valuable information for the neurogenesis during ageing processes.

Musashi1 antigen expression in human fetal germinal matrix development

Musashi1 is a highly conserved protein found in neural progenitor cells. We examined the expression dynamics of Musashi1 in conjunction with other representative neural progenitor antigenic determinants (Ki-67 and nestin) during 8 different stages of the developing human fetal germinal matrix. Our results indicate that Musashi1 is a useful marker for immature cells in periventricular areas inhabited by stem cells, progenitor cells, and differentiating cells.

The subventricular zone releases factors which can be protective in oxygen/glucose deprivation-induced cortical damage: an organotypic study

A number of studies have already established the role of the subventricular zone in sustaining adult neurogenesis in different brain regions and under different pathological conditions, but nothing is reported about the role of this germinal area in preserving cell viability. In this work, we developed an organotypic culture model of the forebrain structures that comprise the neocortex, striatum, subventricular zone, and corpus callosum. With this model, we investigated the role of the subventricular zone in modulating cell viability in the cortex after oxygen/glucose deprivation. Here we have demonstrated that soluble heat-labile factors released by the subventricular zone in the media can lead to protection specifically in the cortical area. No protection was observed when medium, conditioned with factors released during the insult was administered to the hippocampal slices. Moreover, the use of different modifications of the slice cultures showed that the removal of the subventricular zone increased the cellular damage induced by oxygen/glucose deprivation. Furthermore, by using pharmacological experiments to investigate the possible mechanisms that regulate this subventricular function, we found evidence of purinergic involvement. We postulate that extracellular ATP signaling in the subventricular zone exacerbates cortical damage induced by hypoxia/hypoglycemia. For the first time, we demonstrate in vitro that the germinal subventricular zone can release factors that can be protective after exposure to a metabolic stressor. These released factors are not yet characterized but we identified in the extracellular ATP a factor that may interfere with the protective role of the subventricular zone during metabolic cortical damage.

Presence of nerve growth factor and TrkA expression in the SVZ of EAE rats: evidence for a possible functional significance

Nerve growth factor (NGF) is a well-characterized neurotrophic factor that plays a crucial role during development in the growth, differentiation, and maintenance of brain neurons as well as in the reparative response of the adult brain to neuronal damage. Recent studies have shown that acute axonal loss occurs in multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), and that NGF suppresses clinical symptoms of EAE in nonhuman primates. Aim of the present study was to investigate the role of NGF in the regenerative response of the adult brain to neuronal damage occurring in EAE. Using EAE rats, we have found that exogenous NGF injection and NGF deprivation (NGF autoimmunization) can act on growth and differentiation of brain precursor cells in the subventricular zone (SVZ) of EAE rats. Moreover, NGF administration in brain of EAE rats stimulates the expression of early neuronal markers on proliferating precursor cells of the SVZ. The data obtained demonstrated that NGF and its antibody affect bromodeoxyuridine (BrdU) incorporation and NGF receptor expression by SVZ progenitor cells in the brain of EAE rats.

1H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU)

Short echo time single voxel methods were used in previous MR spectroscopy studies of phenylalanine (Phe) levels in phenylketonuria (PKU) patients. In this study, apparent T2 relaxation time of the 7.3-ppm Phe multiplet signal in the brain of PKU patients was assessed in order to establish which echo time would be optimal. 1H chemical shift imaging (CSI) examinations of a transverse plain above the ventricles of the brain were performed in 10 PKU patients and 11 persons not suffering from PKU at 1.5 T, using four echo times (TE 20, 40, 135 and 270 ms). Phe was detectable only when the signals from all CSI voxels were summarized. In patients suffering from PKU the T2 relaxation times of choline, creatine and N-acetyl aspartate (NAA) were similar to those previously reported for healthy volunteers (between 200 and 325 ms). The T2 of Phe in brain tissue was 215 +/- 120 ms (standard deviation). In the PKU patients the brain tissue Phe concentrations were 141 +/- 69 microM as opposed to 58 +/- 23 microM in the persons not suffering from PKU. In the detection of Phe, MR spectroscopy performed at TE 135 or 270 ms is not inferior to that performed at TE 20 or 40 ms (all previous studies). Best results were obtained at TE=135 ms, relating to the fact that at that particular TE, the visibility of a compound with a T2 of 215 ms still is good, while interfering signals from short-TE compounds are negligible.

Increased ICAM-1 and VCAM-1 expression in the brains of autoimmune mice

Pathogenic mechanisms of central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) remain unknown. We recently reported the presence of autoantibodies in the brain tissue ex vivo of autoimmune MRL/lpr mice. We postulated that at least some of these autoantibodies are produced in situ because of B-cell entry into the brain. The blood-brain barrier (BBB) blocks the entry of most large molecules and cells into the brain. In certain CNS pathologies, however, immune cells gain entry due to elevated expression of adhesion molecules. This study looked at adhesion molecule expression, ICAM-1 and VCAM-1, in the brains of MRL/lpr mice. Using immunofluorescent antibody binding assays and confocal laser imaging, we show that expression of ICAM-1 and VCAM-1 is elevated in MRL/lpr mice brains at 4 months of age as compared to age-matched controls. These results suggest a possible mechanism for leukocyte entry into the brains of autoimmune mice that in turn suggest immune-mediated pathology in CNS-lupus.

Neurogenesis and glial proliferation persist for at least one year in the subventricular zone following brain trauma in rats

In several models of traumatic brain injury in rodents, remarkably progressive tissue loss and neuron death has been observed accompanied by expanding ventricles. Here, we explored potential cell proliferation in the subventricular zone (SVZ) in response to this progressive posttraumatic neurodegeneration. Four-month-old rats (n = 57) were subjected to parasagittal fluid-percussion brain injury or sham treatment (no injury), and their brains were harvested at 2 weeks, 2 months, 6 months, and 1 year (n = 6-8/group) after injury or sham treatment. Brain sections (6 microm) were stained with markers of cell proliferation, Ki-67, and proliferative cell nuclear antigen (PCNA) to detect mitotically active cells. In sham animals, we found a typical age-dependent decrease in Ki-67- and PCNA-labelled cells in the SVZ over the course of 1 year. However, in brain-injured animals, this decrease was reversed culminating in a sixfold increase in the number of cells staining with Ki-67 and a threefold increase in cells staining with PCNA by 1 year following injury compared to age-matched controls. Using double labeling, we also determined that many of the cells staining with Ki-67 or PCNA expressed markers selective for neurons (neurofilament protein) and glia (GFAP). These data suggest that there is a persistent proliferation of neurons and glia in the SVZ following brain trauma that does not diminish during aging as found in non-injured animals.

Posthemorrhagic ventricular dilation in the neonate: development and characterization of a rat model

Intraventricular hemorrhage is a common complication of prematurity. Posthemorrhagic ventricular dilation (PHVD) has a high rate of disability and no safe and effective treatment. Its pathogenesis is poorly understood, largely because of the lack of a satisfactory animal model. We have developed a model of neonatal PHVD in the rat. Seven-day-old (P7) Wistar rat pups were given 80-microl injections of citrated rat blood or artificial cerebrospinal fluid (CSF) into alternate lateral ventricles on P7 and P8. Intracranial pressure was monitored and increased briefly by over 8-fold. Some rats received further 10-microl intraventricular injections of India ink on P21. Animals were weighed daily and simple neurologic tests performed. On P21 (or P22 if India ink had been injected), the rats were perfusion-fixed and blocks processed for paraffin histology. Sixty-five percent of pups injected with blood and 50% injected with artificial CSF developed dilated lateral ventricles, with patchy loss of ependyma, marked astrocytic gliosis, and rarefaction of periventricular white matter. India ink injection revealed slow transit of CSF from the dilated lateral ventricles but eventual passage into the subarachnoid space. Pups that had received intraventricular injections but did not develop ventricular dilation nonetheless had lighter brains than littermate controls (p < 0.001). Body weights were not significantly different from controls. Hydrocephalic animals had reduced motor performance as assessed by a grip traction test (p = 0.0002). This model is well suited to studying the pathogenesis of PHVD.

Cerebral cortex lesions decrease the number of bromodeoxyuridine-positive subventricular zone cells in mice

We previously showed that cortical lesions in rats increase the number of subventricular zone (SVZ) cells. Here, we examined the response of the SVZ to cortical lesions in mice from 6 h to 35 days later. Whereas the total number of cells did not change, the number of cells in S-phase (bromodeoxyuridine-positive) decreased in a biphasic manner (from 6 h to day 3, and again at days 25-35). In addition, there was a delayed (days 25-35) increase in immunoreactivity for polysialylated neural cell adhesion molecule, a marker of neuroblasts. The results suggest that in mice there are rapid as well as delayed responses in the SVZ to injury of the overlying cerebral cortex. They also show that the SVZ of different mammalian species can exhibit widely divergent responses to the same brain injury.

Co-localization of GLUT1 and GLUT4 in the blood-brain barrier of the rat ventromedial hypothalamus

The ventromedial hypothalamus (VMH) has been proposed to be a glucose sensor within the brain and appears to play a critical role in initiating the counterregulatory response to hypoglycemia. Transport of glucose across the brain capillaries and into neurons in this region is mediated by different isoforms of the sodium-independent glucose transporter gene family. The objective of the present study was to identify the specific glucose transporter isoforms present, as well as their cellular localization, within the VMH. Immunohistochemistry was performed for GLUT1, GLUT2 and GLUT4 in frozen sections of hypothalami from normal rats. GLUT1 was present on the endothelial cells of the blood-brain barrier (BBB) of the VMH. GLUT2 immunoreactivity was seen in the ependymal cells of the third ventricle and in scattered cells in the arcuate and periventricular nuclei. There was no GLUT2 expression in the VMH. The insulin-sensitive GLUT4 isoform was localized to vascular structures within the VMH. Double-labeled immunohistochemistry demonstrated co-localization of GLUT4 with GLUT1 and with the tight junction protein ZO-1 in the VMH and suggested that VMH GLUT4 expression was restricted to the BBB. The role of GLUT4 in the brain and within the VMH is unknown, but given its location on the BBB, it may participate in brain sensing of blood glucose concentrations.

Differential modulation of proliferation in the neocortical ventricular and subventricular zones

Recent studies have implicated the classical neurotransmitters GABA and glutamate in the regulation of neural progenitor proliferation. We now show that GABA and glutamate have opposite effects on the two neural progenitor populations in the ventricular zones (VZs) and subventricular zones (SVZs) of the embryonic cerebrum. Application of either molecule to organotypic slice cultures dramatically increases proliferation in the VZ by shortening the cell cycle, whereas proliferation in the SVZ is decreased. These disparate effects, measured both by bromodeoxyuridine uptake and the expansion of retrovirally labeled progenitor clones, are mimicked by the application of specific GABA and glutamate agonists and are blocked by antagonists. Thus, the relative contributions of the VZ and SVZ to neocortical growth may be regulated by differential responsiveness to GABA and glutamate.

Glial fibrillary acidic protein-like immunoreactive ependymal elements in the third ventricle of the rat. A study at different stages of development

Using the peroxidase-antiperoxidase method a study was made of the cells immunoreactive to glial fibrillary acidic protein (GFAP) anti-serum in the ependyma of the third ventricle of the rat at different stages of growth. Most of the ependymal cells of the third ventricle were seen to be unreactive to this protein; however, it was sometimes possible to observe some GFAP-immunoreactive ependymocytes and occasionally other immunoreactive cellular types, such as tanycytes and supraependymal cells. Despite this, the most frequent localization of the elements immunoreactive to the protein adopted the shape of an immunoreactive subependymal band situated parallel to the ventricular wall. As the weights of the animals increased an increase in the elements immunoreactive to this protein could be observed in all the zones considered, there being no differences between the male and female animals.

Prevention of stress-induced weight loss by third ventricle CRF receptor antagonist

We previously reported that rats exposed to repeated restraint (3 h/day for 3 days) experience temporary hypophagia and a sustained reduction in body weight compared with nonrestrained controls. Studies described here determined the involvement of central corticotropin-releasing factor (CRF) receptors in the initiation of this chronic response to acute stress. In experiment 1, Sprague-Dawley rats were fitted with cannulas in the lateral ventricle and infused with 50 micrograms of alphahCRF-(9-41) or saline immediately before restraint on each of the 3 days of restraint. The receptor antagonist inhibited hypophagia and weight loss on day 1 of restraint but not on days 2 and 3. In experiment 2, 10 micrograms of alphahCRF-(9-41) or saline were infused into the third ventricle immediately before each restraint. The receptor antagonist totally blocked stress-induced hypophagia and weight loss. These results demonstrate that CRF receptors located in or near the hypothalamus mediate the acute responses to stress that lead to a permanent change in the hormonal or metabolic processes that determine body weight and body composition.

Accelerated release and production of orphanin FQ in brain of chronic morphine tolerant rats

Orphanin FQ has been shown to possess anti-opioid activity at supraspinal level. Our previous work revealed that chronic morphine tolerance could be reversed by intracerebroventricular (i.c.v.) injection of OFQ IgG to rats. In this study, we used radioimmunoassay (RIA) to assess the changes of Orphanin FQ immunoreactivity (OFQ-ir) in cerebroventricular perfusate, periaqueductal gray (PAG) and amygdala of rats made tolerance to morphine (10-60 mg/kg, s.c., t.i.d., for 5 days). The results indicated that: (1) In rats administrated with morphine for 3 and 5 days, the content of OFQ-ir in cerebroventricular perfusate increased by 25% and 52% over the NS control group. (2) The content of OFQ-ir in PAG of rats receiving 1d, 3d and 5d injections of morphine showed an increase of 17%, 48% and 81% respectively over NS group. (3) The content of OFQ-ir in amygdala of rats given 3d and 5d of morphine showed a 36% and 55% increase compared with corresponding control group. It is suggested that continuous use of high doses of morphine accelerated the release and biosynthesis of OFQ in rat brain to antagonize the effect of opioids, which may play a role in the development of morphine tolerance, and that brain OFQ may serve as a delayed negative feedback control on opioid analgesia.

Calcium-binding proteins in the dorsal ventricular ridge of the lizard Psammodromus algirus

The aim of the present work was to study further the intrinsic organization of the dorsal ventricular ridge of lizards. For that purpose, the morphology and distribution of cells and fibers containing the calcium-binding proteins calbindin-D28k, parvalbumin, and calretinin were investigated by using immunohistochemical methods. Colocalization of calcium-binding proteins with the neurotransmitter gamma-aminobutyric acid (GABA) was also studied because they are shown to coexist in many areas of the telencephalon where they define distinct subpopulations of GABAergic local circuit neurons. Neurons containing calcium-binding proteins are limited to the anterior part of the dorsal ventricular ridge (ADVR), whereas the posterior or caudal portion of the ridge is devoid of immunoreactive cells. This result gives further evidence for defining both regions of the dorsal ventricular ridge. Calcium-binding proteins mark three distinct populations of neurons within the ADVR. Two of them, parvalbumin- and calretinin-expressing cells, are GABAergic. On the other hand, calbindin-containing neurons do not express GABA, and the possibility is discussed that these cells are projection neurons. The distribution and overall density of fibers immunoreactive to calcium-binding proteins suggests that most fibers are of extrinsic origin, the thalamic nuclei projecting to the ADVR and the lateral amygdala being good candidates for their origin. The comparison of data on the populations of calcium-binding protein-containing neurons in the reptilian ADVR with those of mammals illustrate the difficulty in finding a mammalian homologue for this controversial region of the reptilian telencephalon.

Clinicopathologic study of 61 patients with ependymoma including MIB-1 immunohistochemistry

Predicting behavior based on histologic appearance has been problematic in ependymomas. Sixty-one patients with ependymoma (excluding subependymoma and myxopapillary ependymoma) were studied. The patients included 36 men and ranged in age from 1.5 to 74 years (median, 33 years). The most common clinical presentations included headache (n = 19), weakness (n = 18), nausea/vomiting (n = 12), and gait disturbance (n = 10). Location included spinal cord (n = 24), fourth ventricle (n = 21), lateral ventricle (n = 8), and third ventricle (n = 5). Initial surgery included a gross total resection of tumor in 22 patients and subtotal resection or biopsy in the remaining patients. Thirty-five patients were known to have been treated with adjuvant radiation therapy and 13 patients received adjuvant chemotherapy. At last known follow-up, 20 patients were alive with no evidence of tumor (median, 66.5 months), 17 patients were alive with residual tumor (median, 14 months), and 12 patients died of tumor (median, 27.5 months). Two additional patients are alive with tumor status not known, two cases are current, and two patients were lost to follow-up. The additional six patients died either shortly after surgery or of surgical complications. Sixteen of 18 patients had at least one tumor recurrence at median 28.5 months. Fifty-one tumors had a predominantly glial pattern and 10 had a mixed glial-epithelial pattern. Of histologic features examined, patients with tumor recurrence or who died of tumor more frequently had observable mitotic figures, vascular proliferation, necrosis, and foci of increased cellularity. Eight of 18 recurrent tumors were classified as high grade ependymomas (anaplastic/malignant). Of patients who died of tumor, 4 of 12 had histologically high grade tumors versus 5 of 39 of the remaining tumors. MIB-1 immunostaining (marker of cell proliferation) was performed on 50 tumors. MIB-1 labeling indices (% positive tumor cell nuclei) ranged from 0.1 to 34.0 (median, 1.1). A higher percentage of patients with recurrent tumor (6 of 13, 46%) or who died of tumor (3 of 10, 30%) had MIB-1 indices >/= 4.0 versus the remaining patients (8 of 33, 24%). The conclusions are as follows: (1) histologic appearance and MIB-1 indices were not reliably predictive of tumor behavior, probably due in part to tumor heterogeneity; (2) tumors with two or more of the following features: identifiable mitotic figures, hypercellularity, vascular proliferation, and necrosis were more likely to behave in an aggressive manner; and (3) elevated MIB-1 labeling indices (>/=4.0 in this study) were encountered in a higher percentage of fatal and recurrent tumors than in nonfatal or nonrecurrent tumors.

Glutamate and taurine are increased in ventricular cerebrospinal fluid of severely brain-injured patients

Glutamate contributes to secondary brain damage, resulting in cell swelling and brain edema. Under in vitro conditions, increased extracellular levels of the amino acid taurine reflect glutamate-induced osmotic cell swelling. In vivo, increases in cerebrospinal fluid (CSF) taurine could, therefore, unmask glutamate-mediated cytotoxic edema formation and possibly differentiate it from vasogenic edema. To test this hypothesis, ventricular CSF glutamate and taurine levels were measured in 28 severely brain-injured patients on days 1, 5, and 14 after trauma. Posttraumatic changes in CSF amino acids were investigated in regard to extent of tissue damage and alterations in brain edema as estimated by computerized tomography. On day 1, CSF glutamate and taurine levels were significantly increased in patients with subdural or epidural hematomas (8+/-0.8/71+/-12 microM), contusions (21+/-4.1/122+/-18 microM), and generalized brain edema (13+/-3.2/80+/-15 microM) compared to lumbar control CSF (1.3+/-0.1/12+/-1 microM; p < 0.001). CSF amino acids, however, did not reflect edema formation and resolution as estimated by computerized tomography. CSF taurine correlated positively with glutamate, eventually depicting glutamate-induced cell swelling. However, parallel neuronal release of taurine with its inhibitory function cannot be excluded. Thus, the sensitivity of taurine in unmasking cytotoxic edema formation is weakened by the inability in defining its origin and function under the conditions chosen in the present study. Overall, persisting pathologic ventricular CSF glutamate and taurine levels are highly suggestive of ongoing glial and neuronal impairment in humans following severe traumatic brain injury.

Galanin receptors in the hippocampus and entorhinal cortex of aged Fischer 344 male rats

Galanin (GAL) has been proposed to be an inhibitory modulator of cholinergic memory pathways because it acts within the hippocampus to inhibit the release and antagonize the postsynaptic actions of acetylcholine. Here we have used: 1) slice binding and quantitative autoradiography to assess the density and occupancy of GAL receptors; and 2) in situ hybridization histochemistry to assess expression of the GALR1 receptor subtype in the ventral hippocampus of 3-month-old and 21-month-old Fischer 344 male rats. We detected a small but significant (p < or = 0.0003) age-related reduction in 125I-GAL binding-site density in the ventral hippocampus and entorhinal cortex under standard binding conditions. Post-hoc analysis indicated that this reduction with age persisted in the CA1 radiatum and entorhinal cortex following GTP-induced desaturation to unmask pre-existent GAL receptors occupied by endogenous ligand. It was not associated with a significant change in peak GALR1 gene expression in the hippocampus. Because a portion of GAL receptors in this region have been postulated to function as presynaptic auto-receptors on cholinergic fiber terminals, the reduction in GAL binding sites with age may be a consequence of age-related alterations in GAL receptor expression by basal forebrain cholinergic neurons which project to the ventral hippocampus.

Quantitative spectroscopic imaging of the human brain

A method to provide B1 correction and cerebrospinal fluid (CSF) referencing is developed and applied to spectroscopic imaging of the human brain at 4.1 T using a volume head coil. The B1 image allows rapid determination of the spatially dependent B1 that is then used to compensate for the B1 sensitivity of the spectroscopic sequence. The reference signal is acquired from CSF located in a lateral ventricular position using a point-resolved echo spectroscopy (PRESS) acquisition. The CSF spectrum is also corrected for B1 dependence. Together with T2 and T1 corrections, this method is used to provide quantitative values of N-acetylaspartate (NAA), creatine (Cr), and choline (Ch). The metabolite concentrations obtained from a spectroscopic imaging slice through the ventricles in seven normal controls are in good agreement with previously published literature values. This method is applied in a patient with secondary progressive multiple sclerosis, showing separate areas of abnormalities in both NAA and Cr.

DNA fragmentation and HSP72 gene expression by adenovirus-mediated gene transfer in postischemic gerbil hippocampus and ventricle

A replication defective adenoviral vector containing the E. coli lacZ gene (AdCMVnLacZ) was directly injected into right hippocampus and lateral ventricle immediately after 5 min of transient global ischemia in gerbils. The relations between the lacZ gene expression and DNA fragmentation or heat shock protein 72 (HSP72) immunoreactivity were examined up to 21 days post ischemia. The lacZ gene was transiently expressed at 1 day in the hippocampus except around the CA1 region, while a large number of the periventricular cells strongly expressed the lacZ gene from 8 h to 7 days. In CA1 layer, terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) positive cells, which were present only adjacent to the needle track at 8 h to 1 day, became more extensive in the whole CA1 layer at 3 to 7 days. TUNEL-positive cells were also detected around the DG at 1 day, around the needle track at 8 h to 3 days, and in the choroid plexus cells at 7 days. HSP72 staining was detected in the subiculum at 1 to 3 days, the dentate granule cells at 8 h to 1 day, and in the CA3 or CA4 pyramidal cells at 1 to 3 days. Some lacZ expressing cells were double-positive with HSP72 in DG, while the majority of those were distinguished from the TUNEL-positive cells. Pyramidal neurons were almost completely lost in the CA1 sector at 7 days after the ischemia. The present study demonstrates the successful LacZ gene transfer into the hippocampus and ventricle of postischemic gerbil brain except in the vulnerable CA1 layer by adenoviral vector injection. However, adenovirus-mediated gene transfer may induce indirect apoptotic cell death in the DG and ventricle, in addition to direct traumatic injury around the needle track.

Exogenous glutamate enhances glutamate receptor subunit expression during selective neuronal injury in the ventral arcuate nucleus of postnatal mice

Administration of high doses of glutamate (Glu) leads to selective neurodegeneration in discrete brain regions near circumventriclular organs of the early postnatal mouse. The arcuate nucleus-median eminence complex (ARC-ME) appears to be the most Glu-sensitive of these brain regions, perhaps because of the intimate relationships between its neurons and specialized astroglial tanycytes. To investigate the mechanism of Glu-induced neuronal loss, we administered graded doses of the sodium salt of glutamate (MSG) to postnatal mice, measured their plasma Glu concentrations, and performed microscopic analyses of the ARC-ME region 5 h after treatment. Nursing, 7-day-old mouse pups (CD1, Charles River, Hollister, Calif.) were injected subcutaneously with single doses of 0.1-0.5 or 1.0-4.0 mg of MSG per g BW, or with water vehicle alone. Mice were decapitated 5 h later and the brains immediately fixed by immersion in buffered aldehydes. Frontal vibratome tissue sections at comparable levels of the ARC-ME were examined by light microscopy. A dose of 4.0 mg MSG/g BW caused neurodegeneration throughout the ARC region, while 1.0 mg/g MSG resulted in less extensive damage. Injection of 0.2 mg MSG/g BW, which raised plasma Glu concentrations 17-fold after 15 min, was the minimum dose tested at which nuclear and cytoplasmic changes were observed in a small group of subependymal neurons near the lateral recesses of the third ventricle. Higher doses of 0.3-0.5 mg MSG caused injury to additional neurons situated farther laterally, but damage remained confined to the ventral region of the ARC nucleus. Ultrastructural examination showed some subependymal neurons with pyknotic nuclei, reduced cytoplasmic volume, and swollen subcellular organelles, while others had fragmented and condensed nuclear material. Immunostaining for tyrosine hydroxylase indicated that dopamine neurons were spared at the threshold dose, but suffered damage after higher doses of MSG. Immunostaining for Glu receptor subtypes revealed that 0.2 mg MSG/g BW enhanced neuronal expression of NMDAR1 and of GluR2/4, and that higher doses of MSG preferentially increased NMDAR1 expression in injured neurons. These results extend previous reports of Glu sensitivity in the ARC-ME region of 7-day postnatal mice. A dose of 0.2 mg MSG/g BW s.c. causes clear but discrete injury to specific subependymal neurons of undetermined phenotype near the base of the third ventricle. Slightly higher doses of MSG evoke damage of additional neurons confined to the ventral region of the ARC traversed by tanycytes. These same greater amounts of MSG promote dose-related increase in the expression of NMDAR1 more than of GluR2/4 in injured ARC neurons, suggesting that elevated Glu receptor levels may contribute to or be related to neuronal cell death. Taken together with previous findings, the data suggest that Glu responsitivity in the ARC-ME of the postnatal mouse may result from transient developmental conditions involving the numerical ratios and juxtaposition between tanycytes and neurons, expression of Glu receptors, and perhaps other ontogenetic factors which may not persist in the mature adult.

Neuronal and glial expression of heparin-binding EGF-like growth factor in central nervous system of prenatal and early-postnatal rat

We investigated heparin-binding epidermal growth factor-like growth factor (HB-EGF) gene and protein expression in the central nervous system of prenatal and early postnatal rats. Assay by northern blot analysis showed that the HB-EGF mRNA was markedly expressed in the brain. In situ hybridization and immunohistochemical techniques showed that concordant expression of HB-EGF mRNA and protein was widely observed in the neurons and interfascicular oligodendrocytes, especially in the cerebellum, the hippocampus, the cerebral cortex, the subventricular area, and the brain stem nuclei. The intense expression of the HB-EGF mRNA was related anatomically and temporally to the proliferating neuroblasts in the external granular layer of the cerebellum and the subventricular layer of the cerebrum. These findings suggest that HB-EGF acts as a mitogen for the neuroblasts. Moreover, HB-EGF expression was observed in the post-mitogenic cells, such as in the cells of the molecular layer, the white matter, the IGL, or the Purkinje cells of the cerebellum. Since EGF receptors are abundantly expressed in the post-mitogenic period, the HB-EGF mRNA expression observed in the post-mitogenic period in our study suggests that HB-EGF also has a non-mitogenic function. These results suggest that HB-EGF significantly contributes to the development of the brain.

Blood-brain barrier penetration of 3-aminopropyl-n-butylphosphinic acid (CGP 36742) in rat brain by microdialysis/mass spectrometry

The detection and quantitation of the novel drug 3-aminopropyl-n-butylphosphinic acid (APBP), also known as CGP 36742, was performed in vivo using microdialysis and tandem mass spectrometry. This drug is a GABA-B antagonist with high specificity for GABA-B receptors. Animals received doses of 100, 200, 500 and 1000 mg kg-1 of the drug either intravenously or per os (p.o.). Microdialysis probes, placed by stereotaxis in either the frontal cortex or third ventricle of the rat, were used to collect dialyzate samples over several hours. Samples were then analyzed by micro-electrospray tandem mass spectrometry to achieve a molecular mass and structure specific analysis. For example, animals receiving a dose of 100 mg kg-1 p.o. showed a peak concentration of approximately 10 microM in the dialyzate. For comparison, tissue and plasma samples of the drug were measured under the same conditions using gas chromatography/mass spectrometry. This work demonstrates that the microdialysis technique in combination with the molecular specificity and high sensitivity of micro-electrospray tandem mass spectrometry can be used to study the time course of the appearance of unmodified drug in the brain of a single animal.

Estrogen receptor and progesterone receptor-immunoreactive cells are not co-localized with gonadotropin-releasing hormone in the brain of the female mink (Mustela vison)

The distribution of gonadal steroid (estrogen, progesterone) receptors in the brain of the adult female mink was mapped by immunocytochemistry. Using a monoclonal rat antibody raised against human estrogen receptor (ER), the most dense collections of ER-immunoreactive (IR) cells were found in the preoptic/anterior hypothalamic area, the mediobasal hypothalamus (arcuate and ventromedial nuclei), and the limbic nuclei (amygdala, bed nucleus of the stria terminalis, lateral septum). Immunoreactivity was mainly observed in the cell nucleus and a marked heterogeneity of staining appeared from one region to another. A monoclonal mouse antibody raised against rabbit uterine progesterone receptor (PR) was used to identify the PR-IR cells in the preoptic/anterior hypothalamic area and the mediobasal hypothalamus (arcuate and ventromedial nuclei). This study also focused on the relationship between cells containing sex-steroid receptors and gonadotropin-releasing hormone (GnRH) neurons on the same sections of the mink brain using a sequential double-staining immunocytochemistry procedure. Although preoptic and hypothalamic GnRH neurons were frequently in close proximity to perikarya containing ER or PR, they did not themselves possess receptor immunoreactivity. The present study provides neuroanatomical evidence that GnRH cells are not the major direct targets for gonadal steroids and confirms for the first time in mustelids the results previously obtained in other mammalian species.

Neurochemistry of brain lesions determined by spectroscopic imaging in systemic lupus erythematosus

OBJECTIVE

The significance and etiology of focal brain lesions in systemic lupus erythematosus (SLE) are unknown. Our purpose was to determine whether the neurochemistry of focal lesions and normal appearing brain tissues in SLE were consistent with neuronal loss, demyelination, or ischemia.

METHODS

Patients with SLE (n = 14) and controls (n = 13) were studied using magnetic resonance imaging (MRI) and spectroscopic imaging (SI) at 1.5 Tesla.

RESULTS

MRI detected fixed focal brain lesions (n = 16) and SI measured brain metabolites, including N-acetylaspartate (NAA), creatine (Cre), choline (Cho), and lactate (Lac). NAA/Cre of normal appearing brain was decreased in patients with SLE compared to controls: grey matter (1.74 +/- 0.16 vs 1.92 +/- 0.18; p = 0.01), occipital white matter (1.98 +/- 0.22 vs 2.23 +/- 0.16; p = 0.004), and periventricular white matter (2.00 +/- 0.23 vs 2.33 +/- 0.23; p = 0.001). Lesions were characterized by markedly decreased NAA/Cre relative to normal appearing tissues in the same patient (1.67 +/- 0.22 vs 1.88 +/- 0.14; p = 0.0002). Elevated Cho/Cre was observed in 25% of focal lesions and 21% of normal appearing tissues. No elevation of lactate was observed in lesions or normal appearing tissues.

CONCLUSION

SI detects focal and generalized brain abnormalities in SLE characterized by decreased NAA, elevated choline, and normal lactate. These findings are consistent with widespread neuronal injury and demyelination, but are not consistent with anaerobic metabolism.

Does a short loop feedback mechanism for the control of luteinizing hormone secretion exist in the ewe?

It is not known whether a short loop feedback mechanism for the regulation of LH exists in sheep. This study on ovariectomized ewes investigated whether a bolus injection (10, 1, and 0.1 microg LH or 1 microg BSA; n 4) or a 3-h continuous infusion of exogenous LH (100 or 1 ng/min; n = 7) into the third ventricle through a permanent indwelling cannula could influence the activity of the GnRH pulse generator, as determined by measurement of endogenous LH secretion. To assess the potential for involvement in a LH short loop feedback system and to estimate the level of LH in the hypothalamic milieu, the concentrations of LH in the peripheral circulation, portal circulation, and third ventricle were measured during an estradiol-induced preovulatory LH surge (n = 4). Neither the bolus nor continuous administration of LH into the third ventricle had any effect on the mean interpulse interval, nadir, pulse amplitude, or circulating level of systemic LH. Furthermore, despite portal LH concentrations being more than 20-fold higher than jugular LH concentrations, LH levels in third ventricular cerebrospinal fluid remained barely detectable and did not reflect dynamic secretory events in the peripheral or hypothalamo-hypophyseal portal blood. These data demonstrate that in ewes, little pituitary LH reaches the third ventricle, and the small amount that does is unable to affect peripheral gonadotropin release. Our study suggests, therefore, that a short loop feedback system for LH does not exist in the ewe.

Elevated 4-hydroxynonenal in ventricular fluid in Alzheimer's disease

4-Hydroxynonenal (4-HNE), an aldehyde by-product of the peroxidation of fatty acids, has been shown to have toxic properties for neurons in culture. In light of increasing evidence that oxidative stress contributes to the neurodegenerative process in Alzheimer's disease (AD), we quantified levels of free and protein-bound 4-HNE in the ventricular fluid from 19 AD subjects and 13 control subjects by high-pressure liquid chromatography and dot-blot immunoassay. Free 4-HNE levels were found to be significantly elevated in the ventricular fluid of AD subjects compared with control subjects (p = 0.0096). These results demonstrate increased lipid peroxidation in AD brain and suggest a role for 4-HNE in the neurodegenerative process.

Relax, a novel rat bHLH transcriptional regulator transiently expressed in the ventricular proliferating zone of the developing central nervous system

A number of basic helix-loop-helix containing proteins have been shown to be required for neural development at different sites or times. Here, Relax, a novel rat basic helix-loop-helix transcriptional regulator, has been isolated and characterized. Analysis of the temporal and spatial distributions shows that the Relax transcripts are detected exclusively in the central nervous system, in discrete regions from embryonic day 11.5 to 18.5. Most strikingly, Relax is expressed along two major boundaries that define the longitudinal axis in the spinal cord and the hindbrain and is a marker of the anterior tip of this axis in the forebrain. Relax-expressing cells are strictly localized in the ventricular zone of the neural tube, where neural progenitors originate. This unique pattern of expression suggests that Relax is involved in neural fate determination.

Electron microscopic observation of delta-opioid receptor-1 in the rat area postrema

The ultrastructural localization of delta-1-opioid-receptor in the rat area postrema was quantitatively studied by pre-embedding avidin-biotin-peroxidase-complex technique. Most of the immunoreactive profiles (67.4%) observed in the present study were axon terminals, whereas the immunopositive dendrites were less (28.3%). Within the axon terminals, the immunoreactivity was found stronger in the dense-cored vesicles than in the small, clear, and round vesicles. Almost 2/3 of the DOR-1 immunoreactive axon terminals had DAB reacted dense-cored vesicles. About half of the immunopositive axon terminals were found to make synapse to dendrites. The dendrites postsynaptic to DOR-1 immunoreactive axon terminals were identified as DOR-1 immunoreactive or not, mainly according to the immunoreactive appearance of the postsynaptic membrane. About half of the DOR-1 immunoreactive dendrites were observed to receive synapse: most of them have their immunoreactivity results at the postsynaptic membranes.

Correlations between ANP concentrations in atria, plasma and cerebral structures and sodium chloride preference in Wistar rats

We determined whether ANP (atrial natriuretic peptide) concentrations, measured by radioimmunoassay, in the ANPergic cerebral regions involved in regulation of sodium intake and excretion and pituitary glad correlated with differences in sodium preference among 40 Wistar male rats (180-220 g). Sodium preference was measured as mean spontaneous ingestion of 1.5% NaCl solution during a test period of 12 days. The relevant tissues included the olfactory bulb (OB), the posterior and anterior lobes of the pituitary gland (PP and AP, respectively), the median eminence (ME), the medial basal hypothalamus (MBH), and the region anteroventral to the third ventricle (AV3V). We also measured ANP content in the right (RA) and left atrium (LA) and plasma. The concentrations of ANP in the OB and the AP were correlated with sodium ingestion during the preceding 24 h, since an increase of ANP in these structures was associated with a reduced ingestion and vice-versa (OB: r = -0.3649, P < 0.05; AP: r = -0.3291, P < 0.05). Moreover, the AP exhibited a correlation between ANP concentration and mean NaCl intake (r = -0.4165, P < 0.05), but this was not the case for the OB (r = 0.2422). This suggests that differences in sodium preference among individual male rats can be related to variations of AP ANP level. Earlier studies indicated that the OB is involved in the control of NaCl ingestion. Our data suggests that the OB ANP level may play a role mainly in day-to-day variations of sodium ingestion in the individual rat.

Loss of basic fibroblast growth factor in the subcommissural organ of old spontaneously hypertensive rats

The immunocytochemical localization of basic fibroblast growth factor (bFGF) was studied in subcommissural organ (SCO) of aged-matched normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats at 10, 14 and 18 months of age using a polyclonal antibody against bFGF. The bFGF-like immunoreactivity (bFGF-ir) was observed in SCO ependymal cells of young and old normotensive rats. However, a progressive loss of bFGF-immunopositive ependymal SCO cells was observed with age in SH rats (27.24, 57.5 and 96.9% in 10, 14 and 18 months old respectively) compared with aged-matched WKY normotensive rats. Considering the potential role of the SCO in sleep regulation and sodium homeostasis, which are altered in essential hypertension, these data show a new neuroendocrine anomaly to be added to the many others previously observed in this rat strain, when they develop hypertension as they get old.

Catecholaminergic and serotoninergic fibres innervate the ventricular system of the hedgehog CNS

Immunocytochemistry with antisera against serotonin (5-HT), dopamine (DA) and noradrenaline (NA) was used to detect monoaminergic (MA) fibres in the ventricular system of the hedgehog Erinaceus europaeus. Light microscopic examination of immunocytochemically stained sections revealed that the ventricular system of the hedgehog is unique among mammals in that the choroid plexuses receive CA axons and that the supraependyma and subependyma of the cerebral ventricles and the spinal central canal are innervated both by serotoninergic and catecholaminergic (CA) fibres. Supraependymal 5-HT axons were generally more abundant and created at places a large number of interconnected basket-like structures, whereas CA fibres were usually directed towards the ventricular lumen. In the lateral ventricles, CA fibres were more numerous in the ependyma lining grey matter, whereas a higher 5-HT innervation density was observed in the area between the corpus callosum and the caudate nucleus or the septum. In the 3rd ventricle, the ependyma of its dorsal part exhibited a higher 5-HT and NA innervation density, whereas DA fibres were preferentially distributed in the ventral half of the basal region. The ependyma lining the cerebral aqueduct displayed a higher MA innervation density in its ventral part. The ependymal wall of the 4th ventricle exhibited an extremely dense 5-HT innervation, mainly in the floor of the ventricle, relatively fewer NA fibres and only sparse DA ones. Few NA and relatively more 5-HT fibres were detected in the ependyma of the central canal. Finally, the circumventricular organs were unevenly innervated by the 3 types of MA fibres. The extensive monoaminergic innervation of the hedgehog ventricular system described here probably reflects a transitory evolutionary stage in the phylogeny of the MA systems with presently unknown functional implications.

bcl-2 protein is increased in the brain from parkinsonian patients

The proto-oncogene bcl-2 is involved in the regulation of cell death and may be able to block apoptosis in neurons through reduced generation of reactive oxygen species (ROS). The bcl-2 product was measured for the first time in brain (caudate nucleus, putamen and cerebral cortex), ventricular cerebrospinal fluid (VCSF), and lumber CSF (LCSF) from control and parkinsonian patients by highly sensitive two-site sandwich enzyme-linked immunosorbent assay (ELISA). The concentrations of bcl-2 in the nigrostriatal dopaminergic regions were significantly higher in parkinsonian patients than those in controls, whereas this product in cerebral cortex showed no significant difference between parkinsonian and control subjects. Neither VCSF nor LCSF from control or parkinsonian subjects contained the bcl-2 product in the detectable amount (< 5 U/ml). Since oxidative stress may be involved in neurogenerative disorders, accumulation of bcl-2 may reflect a mechanism for counterbalancing ROS-mediated damage, or it might represent the impairment of bcl-2-dependent protection from ROS in parkinsonian brain.

Distribution of radioiodinated recombinant human nerve growth factor in primate brain following intracerebroventricular infusion

The distribution of radioiodinated recombinant human nerve growth factor ([125I]rhNGF) was evaluated in adult cynomolgus monkeys following unilateral intracerebroventricular (icv) administration. Animals were cannulated into the right ventricle and recovered for 7 days. Monkeys were infused with 1.2 micrograms of [125I]rhNGF or [125I]rhNGF with a 140-fold excess of rhNGF. Twenty-four hours after infusion, animals were anesthetized and transcardially perfused with an aldehyde fixative. Coronal brain sections were processed for quantitative film autoradiography or for choline-acetyltransferase immunohistochemistry and then emulsion dipped. Specific radiolabel was distributed bilaterally and, with equal density, throughout the basal forebrain and was colocalized with choline acetyltransferase-positive neurons. Specific labeling was also present in the superficial ventral cortex. Nonspecific binding was observed surrounding the ventricles and lining blood vessels. These results demonstrate that unilateral icv infusion is an effective approach for delivering NGF to basal forebrain cholinergic neurons in primates and represents a viable drug delivery strategy for the therapeutic use of NGF in Alzheimer's Disease.

Cortical lesions induce an increase in cell number and PSA-NCAM expression in the subventricular zone of adult rats

The subventricular zone (SVZ) bordering the lateral ventricle is one of the few regions of adult brain that contains dividing cells. These cells can differentiate into neurons in vivo after migration into the olfactory bulb and in vitro in the presence of appropriate growth factors. Little is known, however, about the fate of these cells in vivo after brain injury in adults. We examined cell number and expression of differentiation markers in the SVZ of adult rats after cortical lesions. Aspiration lesions of the sensorimotor cortex in adult rats induced a transient doubling of the number of cells in the SVZ at the level of the striatum without consistent increases in bromodeoxyuridine-labeled cells. Immunoreactivity to the polysialylated neural cell adhesion molecule, expressed by the majority of cells of the SVZ during development, increased dramatically after lesion. In contrast, immunolabeling for molecules found in mature neurons and glia did not increase in the SVZ after lesion, and immunoreactivity for growth factors that induce differentiation of SVZ cells in vitro decreased or remained undetectable, suggesting that lack of appropriate growth factor expression may contribute to the lack of differentiation of the newly accumulated cells in vivo. The data reveal that cells of the SVZ are capable of plasticity in the adult rat after brain injury in vivo and that the newly accumulated cells retain characteristics seen during development.

[Action duality of nitrogen oxide (NO) in experimental African trypanosomiasis]

Patients with human African trypanosomiasis present a major dysruption of the circadian rhythmicity of the sleep-wake cycle, which was also found in rats infected with Trypanosoma brucei brucei (T.b.b.). The alterations in the immune function and nervous system in African trypsanosomiasis led us to investigate the involvement of nitric oxide (NO), a key molecule in immune and neurophysiological mechanisms, in experimental trypanosomiasis. NO was measured in 35 Sprague Dawley rats using differential impulsional voltammetry with a carbon fiber coated with porphyrin-nickel and nafion, ex vivo in the blood and in vivo in the brain. The rats were anaesthetized with sodium chlorate. Infection was performed intraperitoneally (i.p.) with 0.2 ml of a T.b.b. cryostabilate (clone AnTat 1.1E). Blood was collected by an intracardiac puncture with immediate replacement of blood volume (1 ml) in 7 control rats and 8 rats infected since 15 days, before and after i.p. administration of L-ANA (L-arginine-p-nitro-anilide, 100 mg.kg-1, an inhibitor of NO synthase). Brain measures were done in 20 rats (8 controls, and 12 rats infected since 15 or 21 days), in the cortex (H, -0.5 mm; AP, -0.8 mm; L, 1.2 mm) and the lateral ventricle (H,-3.2 mm). In infected rats, blood NO was at 70% of control values (p < 0.001), and L-ANA suppressed the NO signal in all animals (p < 0.0001), demonstrating that the signal originated from NO. Cortical NO was higher than in the ventricle in both control (p < 0.0001) and infected rats (p < 0.001). NO was more elevated in both structures in 15-day-infected rats than in control rats (p < 0.0001), the difference being enhanced in 21-day-infected rats (p < 0.001). L-ANA suppressed the NO signal in 30 to 60 min. These data suggest that NO intervenes in the development of trypanosomiasis in different manners. It is increased in the brain, which remains unexplained, where it may be involved in blood-brain barrier permeation. Conversely, it is decreased in the blood, may be because of macrophage function impairment, which would explain why trypanosomes can multiply in the host.

Stereospecific occurrence of a parkinsonism-inducing catechol isoquinoline, N-methyl(R)salsolinol, in the human intraventricular fluid

N-Methyl(R)salsolinol, an endogenous neurotoxin, has been proposed to be closely involved in the pathogenesis of Parkinson's disease. The selective toxicity to dopaminergic neurons was strictly limited for (R)-enantiomer of N-methylsalsolinol. Its precursor, (R)salsolinol was enzymatically synthesized from dopamine and acetaldehyde in human. However, it has never been examined whether a non-enzymatic reaction produces racemic salsolinol derivatives from dopamine especially in patients under L-DOPA therapy. To clarify the point, their contents were examined in intraventricular fluid from parkinsonian patients administrated with L-DOPA. Only (R)-enantiomer of N-methylsalsolinol and very low concentration of salsolinol could be detected. The results suggest that N-methyl(R)salsolinol synthesis may not depend on dopamine level, but on the activity of enzymes related to its synthesis and/or catabolism. The results are discussed in relation to pathogenesis Parkinson's disease.

Immunoreactivity for apolipoprotein A-IV in tanycytes and astrocytes of rat brain

Immunoperoxidase and immunofluorescence procedures were used to visualize polyclonal antiserum binding to apolipoprotein (apo) A-IV in rat brain. With both methods, tanycytes and astrocytes were labeled throughout both white and gray matter. Within the cells, the labeling was granular and it was confined to the perinuclear zone and proximal regions of the processes. The labeling was abolished by absorption of the primary antiserum with purified apo A-IV but not by absorption with apo E. These results suggest either that apo A-IV is synthesized by astrocytes, or that apolipoprotein that is synthesized in the small intestine or liver is selectively taken up and stored by the astrocytes.

Sodium depletion induces Fos immunoreactivity in circumventricular organs of the lamina terminalis

Acute sodium depletion by peritoneal dialysis (PD) induces c-fos expression in the subfornical organ (SFO) and organum vasculosum laminae terminalis (OVLT), in conscious rats. Fos immunoreactive (Fos-ir) neurons detected by immunohistochemistry first appeared in these nuclei 60 min after PD, increased gradually in the next 4 h and remained high for 27 h following PD. Fos-ir cells were distributed throughout the body of SFO, being the core of the posterior sections preferentially activated, whereas Fos-ir neurons occurred around the periphery of OVLT (annular disposition). When rats were allowed to drink sodium salt (1.8% NaCl) 24 h after PD, there was a marked reversion of the c-fos expression in the OVLT and a comparatively smaller effect in the SFO. Intracerebroventricular infusion of hypertonic CSF (170 mM NaCl) from 30 min before and during 4 h after PD, significantly inhibited the c-fos expression in both nuclei. These results demonstrate that an acute body sodium deficit induces c-fos activity in SFO and OVLT neurons, indicating the special role of these structures in sodium balance regulation. They also show that the sodium-depletion-induced production of Fos in neurons of the lamina terminalis can be modulated by central or systemic reposition of sodium.

Central neurocytoma. A clinicopathological, immunohistochemical and ultrastructural study of 7 cases

Characterised by distinctive clinicopathological features, the central neurocytoma (CN) is an uncommon and possibly under-recognised primary cerebral neuronal neoplasm. We present clinical and pathological details of seven patients with CN. Histological examination revealed a greater diversity of morphological appearances than is typically described in CN. No anaplastic features were identified. Cellular areas resembling both oligodendroglioma and ependymoma were present in all cases, but each tumour also contained stroma rich areas with hyalinised or aneurysmal vessels. Synaptophysin was expressed by all tumours and probably represents the immunohistochemical marker of choice for identifying CN. Distinguishing ultrastructural features included rounded cell bodies separated by numerous cell processes containing microtubules, pleomorphic neurosecretory granules and occasional synapses. Ki-67 immunostaining revealed a low cell proliferation index in each case. The distinction of CN from other pathological mimics can be reliably made using this multiparametric approach to diagnosis. The generally benign behaviour of CN is confirmed, though there was one patient death in the follow-up period of 10-122 months. Aggressive behaviour in this case was not associated with anaplastic histological features.

The reciprocal synaptic relations between enkephalinergic neurons and catecholaminergic neurons in the area postrema

A preembedding double immunostaining technique using antibodies against methionine-enkephalin and tyrosine hydroxylase was used to study synaptic relations between enkephalinergic and catecholaminergic neurons in the area postrema of the rat at the electron microscopic level. The large nuclei-containing cell bodies of the catecholaminergic neurons displayed well-developed Golgi apparatus. The catecholaminergic somata and dendrites received synapses from enkephalinergic axon terminals, and most of the synapses were symmetrical. Occasionally, the catecholaminergic axon terminals were also found to be presynaptic to the enkephalinergic dendrites. Because the enkephalinergic neurons have been reported to be involved in cardiovascular function and the catecholaminergic neurons involved in the vomiting behavior, the synapses observed in this study may provide morphological evidence of the relationship between the vomiting and cardiovascular functions that are triggered in the area postrema.

The use of periodic acid-thiocarbohydrazide-silver protein-physical development (PA-TCH-SP-PD) procedure for the histochemical detection of neutral carbohydrates in the circumventricular organs of the rat

A periodic acid-thiocarbohydrazide-silver protein-physical development (PA-TCH-SP-PD) procedure was applied to the rat circumventricular organs (CVOs), which are known to be specialized structures in the brain. In the rat CVOs, vivid PA-TCH-SP-PD reactions were obtained in the apical surface and cytoplasm of the ependymal cells of the subcommissural organ (SCO) and the epithelial cells in the choroid plexuses (CPs) examined, and similar positive reactions were detected in the vascular walls and perivascular connective tissues in all the CVOs tested. Further, varying intensities of PA-TCH-SP-PD reactions were noted in the neuronal and glial networks of the organum vasculosum laminae terminalis (OVLT), subfornical organ (SFO) and area postrema (AP). The results obtained in the present study indicate that in the rat CVOs the histologic structures mentioned contain varying amounts of neutral carbohydrates and possible histophysiological significances of these carbohydrates in these organs have been discussed with references to their functions.

Electron-microscopic investigations of vasoactive intestinal peptide (VIP)-like immunoreactive terminal formations in the lateral septum of the pigeon

Vasoactive intestinal peptide (VIP)-like immunoreactive terminal fields were examined in the lateral septum of the pigeon by means of immunocytochemistry. According to light-microscopic observations, these projections originated from VIP-like immunoreactive cerebrospinal fluid (CSF)-contacting neurons, which are located in the ependymal layer of the lateral septum and form a part of the lateral septal organ. The processes of these cells gave rise to dense terminal-like structures in the lateral septum. Pre-embedding immuno-electron microscopy revealed that VIP-like immunoreactive axon terminals had synaptoid contacts with perikarya of small VIP-immunonegative neurons of the lateral septum, which were characterized by an invaginated nucleus, numerous mitochondria, a well-developed Golgi apparatus, endoplasmic reticulum and a small number of dense-core vesicles (about 100 nm in diameter). VIP-like immunoreactive axons were also seen in contact with immunonegative dendrites in the lateral septum. In both axosomatic and axodendritic connections, VIP-like immunoreactive presynaptic terminals contained large dense-core vesicles, clusters of small vesicles and mitochondria. These findings suggest that VIP-immunoreactive neurons of the lateral septal organ project to small, presumably peptidergic nerve cells of the lateral septum and that the VIP-like neuropeptide serves as a neuromodulator (-transmitter) in this area.

Neuropeptides in the human dorsal vagal complex: an immunohistochemical study

The distribution of twelve biologically active neuropeptides, i.e., thyrotropin-releasing hormone, corticotropin-releasing factor, pro-opiomelanocortin-derived peptides (adrenocorticotropic hormone, beta-endorphin, alpha-melanocyte-stimulating hormone), leucine-enkephalin, dynorphin A, dynorphin B, cholecystokinin, substance P, galanin and calcitonin gene-related peptide, was examined by immunohistochemistry in the human dorsal vagal complex including the nucleus of the solitary tract, the dorsal motor nucleus of the vagus and the area postrema. Immunoreactivity of all the twelve neuropeptides was found widely distributed in the various subdivisions of the nucleus of the solitary tract, showing a unique distribution for every peptide. Neuronal cell bodies immunostained with leucine-enkephalin, galanin and dynorphin B were found in this region. There were no immunopositive perikarya for any of the peptides in the other structures studied. Fibers containing galanin, corticotropin-releasing factor, substance P, dynorphin B, thyrotropin-releasing hormone and calcitonin gene-related peptide were observed at a relatively high density in the nucleus of the solitary tract. In the same structure, a moderately dense network of fibers immunostained with dynorphin A, cholecystokinin and leucine-enkephalin, but only solitary pro-opiomelanocortin-derived peptides-containing fiber fragments were observed. In the dorsal motor nucleus of the vagus the most prominent network of fibers was found to contain thyrotropin-releasing hormone, galanin and substance P. In contrast to these, no beta-endorphin immunoreactivity was detected. The area postrema contained only moderate to low densities of galanin-, substance P-, calcitonin gene-related peptide-, dynorphin B- and cholecystokinin-immunoreactive fibers.

[1H-MR spectroscopic imaging: an approach to evaluating alcohol breakdown in the brain]

The local alcohol concentration in the human brain was determined in 10 cases using MR spectroscopic imaging. Therefore 7 subjects with an average blood alcohol concentration of 0.8/000 were examined after oral intake of alcoholic beverages. Varying alcohol concentration was found intracranially which was recorded spectroscopically w.r.t. time. Relatively high ethanol concentrations were determined in the cerebellum as well as in the ventricular system. Contrary to this, lower concentrations were found in the regions of grey and white matter.

Rat FGF receptor-4 mRNA in the brain is expressed preferentially in the medial habenular nucleus

The fibroblast growth factor (FGF) receptor family consists of four members, FGFR-1, FGFR-2, FGFR-3 and FGFR-4, that are closely related receptor tyrosine kinases. We examined the expression of rat FGFR-4 mRNA in the brain by in situ hybridization and compared it with that of the mRNAs for other FGF receptors. In contrast with FGFR-1, FGFR-2 and FGFR-3 mRNAs which are expressed widely in the brain, the FGFR-4 mRNA in the brain is expressed preferentially in the medial habenular nucleus neurons. The present finding indicates that FGFR-4 has a function specific to the medial habenular nucleus.