Glutamate in cerebral tissue of asphyxiated neonates during the first week of life demonstrated in vivo using proton magnetic resonance spectroscopy

We tested the hypothesis that glutamate (Glx) levels as demonstrated by proton magnetic resonance spectroscopy ((1)H-MRS) are elevated in brain tissue of neonates with severe hypoxic-ischemic encephalopathy (HIE). Studies were performed in 26 neonates (median gestational age 40.5 weeks, range 36.7-42.4 weeks; median birth weight 3,360 g, range 2,180-4,200 g). The median postnatal age at the time of testing was 2.5 days (range 1-7 days). HIE was scored according to Sarnat as grade I (n = 4), grade II (n = 15) or grade III (n = 7). Results for neonates with mild to moderate HIE (group 1) were compared to those with severe HIE (group 2). After magnetic resonance imaging, (1)H-MRS was performed in a single volume of interest including the basal ganglia. An echo time of 31 ms was used. After curve-fitting procedures, peak area ratios of different brain metabolites were calculated. The median total Glx/N-acetylaspartate ratio was 1.21 (range 0.64-3.25) in group 1 versus 1.55 (range 1.10-2.75) in group 2 (p = 0.035). The median total Glx/choline ratio was 1.33 (range 0.71-2.52) in group 1 versus 2.14 (range 1.21-3.55) in group 2 (p = 0.019). We concluded that during the first days of life, Glx was elevated in the basal ganglia of neonates with severe HIE.

Spatial distribution, cellular integration and stage development of Parkin protein in Xenopus brain

Parkin is an ubiquitin-protein ligase molecule abundantly expressed in mammalian brains. Deletional mutations of Parkin protein produce a disease-related parkinsonian phenotype which is inherited with an autosomal recessive mode of transmission. To gain a greater insight into the evolutionary trajectory of the protein among vertebrate species, we describe here the (i) distribution pattern, (ii) sizing of specific fragments and (iii) embryonic development of Parkin in Xenopus laevis utilizing two antibodies to the N- and C-terminal sequence of the human Parkin protein. Parkin immunoreactivity was distributed in a heterogeneous fashion throughout the adult frog brain. The telencephalon, including the olfactory bulb, striatum and nucleus accumbens, harbored high numbers of Parkin-containing cells. High numbers of immunoreactive neurons were also present in discrete regions of the thalamus and hypothalamus. Relatively moderate expression of Parkin protein was noted in the nucleus anterodorsalis tegmenti, nucleus reticularis medius and torus semicircularis. The substantia nigra exhibited a distinctive heterogeneous pattern of Parkin-immunoreactivity, especially within presumptive dopamine neurons. The cerebellum also showed high expression of Parkin-positive material. Characterization of the subcellular distribution of the protein indicated both a cytoplasmic and nuclear integration of Parkin-immunoreactivity. This pattern of subcellular localization was similar to that observed in human brain material, perhaps reflecting distinct structural phosphorylation sites of the Parkin protein. Western blot analysis identified three specific bands with molecular weights varying from 50 to 65 kDa in adult Xenopus brain. However, studies on the temporal expression of Parkin during development showed a complete absence of cellular immunoreactivity which was especially conspicuous during late premetamorphic stages of frog development. These results suggest that the ubiquitination activity of Parkin is limited or non-existent during embryogenesis, but appears to assume a more functional role during adulthood as reflected by the high distribution pattern of the protein within major circuits of the amphibian brain.

Synthesis and dopaminergic properties of the two enantiomers of 3-(3,4-dimethylphenyl)-1-propylpiperidine, a potent and selective dopamine D4 receptor ligand

The synthesis of the two enantiomers of 3-(3,4-dimethylphenyl)-1-propylpiperidine 1, a potent and selective D4 dopaminergic ligand, was performed. The 3-(3,4-dimethylphenyl)- 1-propylpiperidine with the R configuration showed an affinity for the D4 receptors 6-fold higher than the corresponding enantiomer with the S configuration. Furthermore, the (R)-1 enantiomer proved to be highly selective for D4 receptors with respect to D2-D3 receptors, with a Ki ratio higher than 25,000, while the (S)-1 enantiomer was about 100-fold less selective than the (R)-1 one.

Altered serotonin and dopamine metabolism in the CNS of serotonin 5-HT(1A) or 5-HT(1B) receptor knockout mice

Measurements of serotonin (5-HT), dopamine (DA), and noradrenaline, and of 5-HT and DA metabolites, were obtained by HPLC from 16 brain regions and the spinal cord of 5-HT(1A) or 5-HT(1B) knockout and wild-type mice of the 129/Sv strain. In 5-HT(1A) knockouts, 5-HT concentrations were unchanged throughout, but levels of 5-HT metabolites were higher than those of the wild type in dorsal/medial raphe nuclei, olfactory bulb, substantia nigra, and locus coeruleus. This was taken as an indication of increased 5-HT turnover, reflecting an augmented basal activity of midbrain raphe neurons and consequent increase in their somatodendritic and axon terminal release of 5-HT. It provided a likely explanation for the increased anxious-like behavior observed in 5-HT(1A) knockout mice. Concomitant increases in DA content and/or DA turnover were interpreted as the result of a disinhibition of DA, whereas increases in noradrenaline concentration in some territories of projection of the locus coeruleus could reflect a diminished activity of its neurons. In 5-HT(1B) knockouts, 5-HT concentrations were lower than those of the wild type in nucleus accumbens, locus coeruleus, spinal cord, and probably also several other territories of 5-HT innervation. A decrease in DA, associated with increased DA turnover, was measured in nucleus accumbens. These changes in 5-HT and DA metabolism were consistent with the increased aggressiveness and the supersensitivity to cocaine reported in 5-HT(1B) knockout mice. Thus, markedly different alterations in CNS monoamine metabolism may contribute to the opposite behavioral phenotypes of these two knockouts.

Tau-positive neurons in corticobasal degeneration and Alzheimer's disease--distinction by thiazin red and silver impregnations

Thiazin red (TR), a fluorochrome that has an affinity to fibrillary structures such as neurofibrillary tangles (NFTs) or senile plaques, was utilized to investigate assembly of tau protein into fibrils in tau-immunopositive neocortical neurons of corticobasal degeneration (CBD) and of Alzheimer's disease (AD). Double fluorescence with anti-paired helical filament monoclonal antibody (AT8) and TR was followed by either the Gallyas or Bodian silver impregnation method, which enabled a comparison of the staining features by three different methods on the same neuron. NFTs of AD were uniformly stained by TR and Gallyas method. Most of tau-immunopositive neurons of CBD were similarly stained by Gallyas method but barely or only weakly by TR or Bodian method, suggesting that tau in neocortical neurons of CBD is less liable to form fibrillary structures than in those of AD, easily distinguishable by TR staining. Clarifying the process of tau assembly using this fluorochrome will give a clue to understanding mechanisms of tau deposition, which may be different in various neurological disorders.

System design for in vivo neutron activation analysis measurements of manganese in the human brain: based on Monte Carlo modeling

Manganese is an essential nutrient required by the human body, but conversely, over exposure to the element may cause central nervous system damage. The technique of in vivo neutron activation analysis, using the McMaster KN-accelerator, is being investigated as a possible method of noninvasively determining manganese concentrations within the human body. Since the brain is the primary target of damage from exposure it would be the ideal site for measurements. Thus, Monte Carlo simulations have been undertaken to define the optimum experimental parameters for such a measurement, examining the use of possible moderator, reflector and collimator materials.

Dopaminergic innervation of the subthalamic nucleus in the normal state, in MPTP-treated monkeys, and in Parkinson's disease patients

The existence of a dopaminergic innervation of the subthalamic nucleus (STN) has been demonstrated in rats but has remained controversial in primates. The aim of the present study was first to demonstrate the existence of a dopaminergic innervation of the STN in monkeys using tracing methods and then to quantify the loss of dopaminergic fibers in the parkinsonian state in monkeys and humans. Following injection of Fluoro-Gold into the STN of a vervet monkey (Cercopithecus aethiops), retrogradely labeled neurons were found to be scattered in all dopaminergic areas of the mesencephalon. Injection of biotin dextran amine into dopaminergic areas A8 and A9 of two monkeys resulted in anterogradely labeled axons located throughout the whole extent of the STN. Labeled axons that also expressed tyrosine hydroxylase (TH) were reconstructed from serial sections. Some terminal axonal arborizations had profuse branching and occupied much of the STN, and others were restricted to small portions of the nucleus. In TH-immunoreactive sections, numerous sparse, fine, and varicose TH-positive fibers were observed in the STN of normal monkeys and humans. Quantification of these TH-positive fibers revealed a 51% loss of TH-positive fibers in MPTP-intoxicated monkeys and a 65% loss in Parkinson's disease patients compared with their respective controls. These findings demonstrate the existence of a dopaminergic innervation of the STN in primates. The loss of dopaminergic innervation in MPTP-intoxicated monkeys and in Parkinson's disease patients may directly affect the activity of STN neurons and could participate in the hyperactivity of the structure.

Localization of nicotinic receptor subunit mRNAs in monkey brain by in situ hybridization

Nicotinic receptors are implicated in memory, learning, locomotor activity, and addiction. Identification of the specific receptor subtypes that mediate these behaviors is essential for understanding their role in central nervous system (CNS) function. Although expression of nicotinic receptor transcript has been studied in rodent brain, their localization in the monkey CNS, which may be a better model for the human brain, is not yet known. We therefore investigated the distribution of alpha4, alpha6, alpha7, beta2, beta3, and beta4 receptors subunit mRNAs in the monkey brain by using in situ hybridization. alpha4 and alpha7 mRNAs were very widely expressed, with a substantial degree of overlap in their distribution, except for the reticular nucleus of the thalamus in which alpha7 mRNA was much more prominently expressed. beta2 and beta4 mRNA were also widely distributed, although beta4 was more prominently localized in thalamic nuclei than beta2. The distribution of alpha6 and beta3 mRNA was very distinct from that of the other transcripts, being restricted to catecholaminergic nuclei, the cerebellum, and a few other areas. Although there were similarities in distribution of the nicotinic receptor subunit mRNAs in monkey and rodent brain, there were prominent differences in areas such as the caudate, putamen, locus coeruleus, medial habenula, and cerebellum. In fact, the distribution of alpha4 and alpha7 mRNAs in the monkey caudate and putamen was more similar to that reported in the human than rodent brain. These findings have implications for the development of drug therapies for neurological disorders, such as Alzheimer's and Parkinson's disease, in which nicotinic receptors are decreased.

Induction of cell-cycle regulators in simian immunodeficiency virus encephalitis

Neuronal degeneration associated with human immunodeficiency virus encephalitis has been attributed to neurotoxicity of signaling molecules secreted by activated, infected macrophages. We hypothesized that the barrage of signals present in the extracellular milieu of human immunodeficiency virus-infiltrated brain causes inappropriate activation of neuronal cell-cycle machinery. We examined the presence of three members of the cell-cycle control machinery: pRb, E2F1, and p53 in the simian immunodeficiency virus encephalitis (SIVE) model. Compared to noninfected and simian immunodeficiency virus-infected, nonencephalitic controls, we observed increased protein expression of E2F1 and p53 and aberrant cellular localization of E2F1 and pRb. In SIVE, E2F1 was abundant in the cytoplasm of neurons in both neurons and astrocytes proximal to SIVE pathology in the basal ganglia. pRb staining was nuclear and cytoplasmic in cortical neurons of SIVE cases. Antibodies to phosphorylated pRb also labeled the cytoplasm of cortical neurons. These data suggest that in SIVE, cell signaling results in phosphorylation of pRb which may result in subsequent alteration in E2F1 activity. As increased E2F1 and p53 activities have been linked to cell death, these data suggest that the neurodegeneration in SIVE could in part be because of changes in expression and activity of cell-cycle machinery.

Differential expression and regional distribution of steroid receptor coactivators SRC-1 and SRC-2 in brain and pituitary

Members of the p160 family of steroid receptor coactivator proteins mediate the stimulatory effects on gene transcription brought about by nuclear receptors, which comprise all steroid receptors. Using in situ hybridization we have examined the neuroanatomical distribution of the messenger RNAs (mRNAs) for two functionally distinct splice variants of Steroid Receptor Coactivator 1 (SRC-1/NCoA-1) and of Steroid Receptor Coactivator 2 (SRC-2/NCoA-2/GRIP-1/TIF-2). Transcripts encoding these coactivators show highly differential expression patterns. SRC-2 mRNA is expressed at very low levels in brain, but shows expression in the anterior pituitary. SRC-la and le mRNA are expressed in many brain areas, including hippocampus, amygdala, hypothalamus, basal ganglia, and isocortex. Striking differences between SRC-1a and le expression were observed in several brain nuclei. Relative levels of SRC-1a mRNA were much higher in anterior pituitary, and the arcuate, paraventricular and ventromedial nucleus of the hypothalamus, the locus coeruleus and the trigeminal motor nucleus, all important targets of steroid hormones in the brain. SRC-le mRNA showed modest elevation of relative expression in the caudal nucleus accumbens (shell), basolateral amygdala, and some thalamic nuclei. The differential and uneven neuroanatomical distribution of these coactivators may underlie diversity and cell-specificity of steroid receptor mediated signals in the brain.

PCR detection of host and HIV-1 sequences from archival brain tissue

Mutations in CCR5 and CCR2b have been recently shown to affect disease progression towards AIDS. A role for these host genotypes in AIDS dementia complex (ADC) has also been postulated but remains unclear. Additionally, brain-derived envelope sequences from HIV-1 have been associated with ADC but their specific contribution to pathogenesis remains uncertain. This study demonstrates the successful use of PCR techniques to isolate host CCR5 and CCR2b, and HIV-1 V3 sequences from paraffin embedded tissues from patients with and without ADC. PCR amplification from archival tissue offers a novel approach for studying the interactions between potential neuroprotective elements in the host and virulence determinants in HIV that may contribute to differences in susceptibility to ADC.

Substance P immunoreactivity in Rett syndrome

Severe autonomic dysfunction occurs in Rett syndrome (RS). Substance P, a tachykinin peptide that localizes to several brain regions, including the autonomic nervous system, is reduced in the cerebrospinal fluid of patients with RS. The anatomic localization and intensity of substance P immunoreactivity and glial fibrillary acidic protein-positive astrocytes in the brains of 14 patients with RS were compared with those in the brains of 10 age-matched normal patients. Substance P immunoreactivity expression was significantly decreased in RS tissue compared with control tissue in the following regions: dorsal horns, intermediolateral column of the spinal cord, spinal trigeminal tract, solitary tract and nucleus, parvocellular and pontine reticular nuclei, and locus ceruleus. A less significant decrease of substance P immunoreactivity occurred in the substantia nigra, central gray of the midbrain, frontal cortex, caudate, putamen, globus pallidus, and thalamus. Antiglial fibrillary acidic protein-positive astrocytes were increased in the areas in which substance P immunoreactivity was decreased and in other brain regions. Because many of the brain regions with the greatest decrease in substance P immunoreactivity are involved in the control of the autonomic nervous system, especially the solitary tracts and reticular formation, reduced substance P may contribute to the autonomic dysfunction in RS.

In vivo NMDA/dopamine interaction resulting in Fos production in the limbic system and basal ganglia of the mouse brain

Glutamatergic and dopaminergic effects on molecular processes have been extensively investigated in the basal ganglia. It has been demonstrated that NMDA and dopamine D(1) and D(2) receptors interact in the regulation of signal transduction and induction of transcription factors. In the present experiments, NMDA/dopamine interactions were investigated in the normosensitive caudate nucleus, hippocampus and amygdala by monitoring Fos production. We demonstrated that NMDA and the D(1) receptor agonist SKF 38393 triggered Fos levels in a distinct, non-overlapping and region-specific pattern. NMDA injected intraperitoneally (i.p.) elevated Fos levels in all hippocampal subfields and the central amygdala, whereas SKF 38393 triggered Fos production in basomedial, cortical, medial amygdala and caudate nucleus. The NMDA receptor antagonist CGS 19755 prevented NMDA- and SKF 38393-triggered Fos production in all investigated brain areas. Similarly, the D(1) receptor antagonist SCH 23390 inhibited the effects produced by SKF 38393 or NMDA. The D(2) receptor antagonist sulpiride exerted synergistic and antagonistic effects on NMDA- and SKF 38393-triggered Fos production, in a region specific manner. These data suggest that NMDA and dopamine receptors regulate Fos production within the limbic system and basal ganglia through regionally differentiated but interdependent actions.

Plasminogen activation in focal cerebral ischemia and reperfusion

In focal cerebral ischemia the plasminogen-plasmin system plays a role in the fibrinolysis of vessel-occluding clots and also in the proteolysis of extracellular matrix components, which potentially contributes to brain edema and bleeding complications. The authors investigated the plasminogen activation after middle cerebral artery occlusion with and without reperfusion (reperfusion intervals 9 and 24 hours) in rats by histologic zymography and compared areas of increased plasminogen activation to areas of structural injury, which were detected immunohistochemically. After 3 hours of ischemia, increased plasminogen activation was observed in the ischemic hemisphere. The affected area measured 5.2%+/-8.5% and 19.4%+/-30.1% of the total basal ganglia and cortex area, respectively. Reperfusion for 9 hours after 3 hours of ischemia led to a significant expansion of plasminogen activation in the basal ganglia (68.8%+/-42.2%, P < 0.05) but not in the cortex (43.0%+/-34.6%, P = 0.394). In the basal ganglia, areas of increased plasminogen activation were related to areas of structural injury (r = 0.873, P < 0.001). No such correlation was found in the cortex (r = 0.299, P = 0.228). In this study, increased plasminogen activation was demonstrated early in focal cerebral ischemia. This activation may promote early secondary edema formation and also secondary hemorrhage after ischemic stroke.

Maze learning and motor activity deficits in adult mice induced by iron exposure during a critical postnatal period

Newborn mice were administered Fe(2+) (iron succinate: 7.5 mg/kg, b. wt) on either Days 3-5, 10-12 or 19-21, or vehicle (saline) at the same times, postnatally. Spontaneous motor behaviour and radial arm maze learning were tested at the age of 3 months. It was found that mice treated with Fe(2+) during postnatal Days 10-12 were markedly hypokinetic during the 1st 20-min test period and hyperkinetic during the 3rd and final 20-min test period. These mice showed an almost complete lack of habituation of spontaneous motor activity parameters to the test chambers. In the radial arm maze, the Days 10-12 treatment group evidenced significantly both more errors in arm choices and longer latencies to acquire all eight pellets; these mice showed also a severe trial-to-trial retention deficit as indexed by retention quotients. These behavioural deficits were observed also in animals treated with Fe(2+) during postnatal Days 3-5, but the effects were less pronounced, indicating the higher susceptibility of the brain for Fe(2+)-induced damage during Days 10-12 postpartum. Treatment with Fe(2+) on Days 19-21 did not induce behavioural alterations in comparison with its respective control (vehicle) group. Analysis of total brain iron content indicated significantly more iron (microg/g) accumulation in the basal ganglia, but not frontal cortex, of mice from the Days 3-5 and 10-12 Fe(2+) (7.5 mg/kg) treatment groups. The contribution of iron overload during the immediate postnatal to later functional deficits seems to implicate symptoms of Parkinsonism but the kinetics of iron uptake to the brain and its regional distribution at this critical period of development awaits elucidation.

In vivo evaluation of brain iron in Alzheimer disease using magnetic resonance imaging

BACKGROUND

The basal ganglia contain the highest levels of iron in the brain, and postmortem studies indicate a disruption of iron metabolism in the basal ganglia of patients with Alzheimer disease (AD). Iron can catalyze free radical reactions and may contribute to oxidative damage observed in AD brains. Treatments aimed at reducing oxidative damage have offered novel ways to delay the rate of progression and could possibly defer the onset of AD. Brain iron levels were quantified in vivo using a new magnetic resonance imaging method.

METHODS

Thirty-one patients with AD and 68 control subjects participated in this study. A magnetic resonance imaging method was employed that quantifies the iron content of ferritin molecules (ferritin iron) with specificity through the combined use of high and low field-strength magnetic resonance imaging instruments. Three basal ganglia structures (caudate, putamen, and globus pallidus) and one comparison region (frontal lobe white matter) were evaluated.

RESULTS

Basal ganglia ferritin iron levels were significantly increased in the caudate (P = .007; effect size, 0.69) and putamen (P = .008; effect size, 0.67) of AD subjects, with a trend toward an increase in the globus pallidus (P = .13). The increased basal ganglia ferritin iron levels were not a generalized phenomenon; white matter ferritin iron levels were unchanged in patients with AD (P = .50).

CONCLUSIONS

The data replicate and extend prior results and suggest that basal ganglia ferritin iron levels are increased in AD. Prospective studies are needed to evaluate whether premorbid iron levels are increased in individuals who develop AD.

Regional brain distribution of noradrenaline uptake sites, and of alpha1-alpha2- and beta-adrenergic receptors in PCD mutant mice: a quantitative autoradiographic study

The mouse "Purkinje cell degeneration" (pcd) is characterized by a primary loss of Purkinje cells, as well as by retrograde and secondary partial degeneration of cerebellar granule cells and inferior olivary neurons; this neurological mutant can be considered as an animal model of human degenerative ataxia. To determine the consequences of this cerebellar pathology on the noradrenergic system, noradrenaline transporters as well as alpha1-, alpha2- and beta-adrenergic receptors were evaluated by quantitative ligand binding autoradiography in adult control and pcd mice using, respectively, [3H]nisoxetine, [3H]prazosin, [3H]idazoxan and [3H]CGP12177. In cerebellar cortex and deep nuclei of pcd mutants, [3H]nisoxetine labelling of noradrenaline transporters was higher than in control mice. However, when binding densities were corrected by surface area, they remained unchanged in the cerebellar cortex but associated with 25% and 40% lower levels of labelling of alpha1 and beta receptors, as well as a very important increase (275%) of alpha2 receptors. In deep cerebellar nuclei, surface corrections did not reveal any changes either in transporter or in receptor densities. Higher densities of [3H]nisoxetine labelling were found in several regions related with the cerebellum, namely inferior olive, inferior colliculus, vestibular, reticular, pontine, raphe and red nuclei, as well as in primary motor and sensory cerebral cortex; they may reflect an increased noradrenergic innervation related to motor adjustments for the cerebellar dysfunction. Increased [3H]nisoxetine labelling was also measured in vegetative brainstem regions and in dorsal hypothalamus, implying altered autonomic functions and possible compensation in pcd mutants. Other changes found in extracerebellar regions affected by the mutation, such as thalamus and the olfactory system implicated both noradrenaline transporters and adrenergic receptors. In contrast to the important alterations of the noradrenergic system in cerebellar cortex, the lack of receptor changes in deep cerebellar nuclei suggests that local adaptations may be sufficient to minimize the consequence of the cerebellar atrophy on motor control. An intense labelling by [3H]idazoxan of the inner third of the molecular layer was a novel, albeit unexplained finding, and could represent a postsynaptic subset of alpha2-adrenergic receptors.

Regional and cellular localisation of GABA(A) receptor subunits in the human basal ganglia: An autoradiographic and immunohistochemical study

The regional and cellular localisation of gamma-aminobutyric acid(A) (GABA(A)) receptors was investigated in the human basal ganglia using receptor autoradiography and immunohistochemical staining for five GABA(A) receptor subunits (alpha(1), alpha(2), alpha(3), beta(2, 3), and gamma(2)) and other neurochemical markers. The results demonstrated that GABA(A) receptors in the striatum showed considerable subunit heterogeneity in their regional distribution and cellular localisation. High densities of GABA(A) receptors in the striosome compartment contained the alpha(2), alpha(3), beta(2, 3), and gamma(2) subunits, and lower densities of receptors in the matrix compartment contained the alpha(1), alpha(2), alpha(3), beta(2,3), and gamma(2) subunits. Also, six different types of neurons were identified in the striatum on the basis of GABA(A) receptor subunit configuration, cellular and dendritic morphology, and chemical neuroanatomy. Three types of alpha(1) subunit immunoreactive neurons were identified: type 1, the most numerous (60%), were medium-sized aspiny neurons that were immunoreactive for parvalbumin and alpha(1), beta(2,3), and gamma(2) subunits; type 2 (38%) were medium-sized to large aspiny neurons immunoreactive for calretinin and alpha(1), alpha(3), beta(2,3), and gamma(2) subunits; and type 3 (2%) were large sparsely spiny neurons immunoreactive for alpha(1), alpha(3), beta(2,3), and gamma(2) subunits. Type 4 neurons were calbindin-positive and immunoreactive for alpha(2), alpha(3), beta(2,3), and gamma(2) subunits. The remaining neurons were immunoreactive for choline acetyltransferase (ChAT) and alpha(3) subunit (type 5) or were neuropeptide Y-positive with no GABA(A) receptor subunit immunoreactivity (type 6). The globus pallidus contained three types of neurons: types 1 and 2 were large neurons and were immunoreactive for alpha(1), alpha(3), beta(2,3), and gamma(2) subunits and for parvalbumin alone (type 1) or for both parvalbumin and calretinin (type 2); type 3 neurons were medium-sized and immunoreactive for calretinin and alpha(1), beta(2, 3), and gamma(2) subunits. These results show that the subunit composition of GABA(A) receptors displays considerable regional and cellular variation in the human striatum but are more homogeneous in the globus pallidus.

Localization of metabotropic glutamate receptor 7 mRNA and mGluR7a protein in the rat basal ganglia

Metabotropic glutamate receptors (mGluRs) coupled to G-proteins have important roles in the regulation of basal ganglia function. We have examined the localization of the mGluR7 mRNA and mGluR7a protein in the basal ganglia of the rat. Strong mGluR7 hybridization signals are found in cerebral cortex and striatum, but much less intense signals are present in other components of the basal ganglia. Abundant mGluR7a immunoreactivity was found in striatum, globus pallidus (GP), and substantia nigra pars reticulata (SNr). Examination using confocal microscopy together with dendritic and presynaptic markers as well as studies in lesion models provided evidence for the presence of mGluR7a on presynaptic terminals in all three structures. Electron microscopic studies confirmed the presence of mGluR7a in axon terminals in both the striatum and the GP and also revealed the presence of mGluR7a at postsynaptic sites in both of these regions. Our data demonstrate that mGluR7a is located not only on presynaptic glutamatergic terminals of the corticostriatal pathway, where it may serve as an autoreceptor, but also on terminals of striatopallidal and striatonigral projections, where it may modulate the release of gamma-aminobutyric acid (GABA). The presence of mGluR7 at these multiple sites in the basal ganglia suggests that this receptor has a particularly crucial role in modulating neurotransmitter release in major basal ganglia pathways.

Correlation of basal ganglia magnetic resonance spectroscopy with Apgar score in perinatal asphyxia

BACKGROUND

Brain metabolite levels are measured by proton magnetic resonance spectroscopy (1H MRS) and include N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lactate and the ratios NAA to Cho and Cr (NAA-ChoCr), NAA-Cr, NAA-Cho, and Cho-Cr. Brain metabolite levels may correlate with the degree of neonatal asphyxia.

OBJECTIVE

To determine which brain metabolite ratios have the strongest correlation with the Apgar scores in infants with possible asphyxia; whether the correlation is stronger with basal ganglia (BG) or anterior border-zone metabolites; and whether a combined approach using routine MR imaging (MRI), diffusion-weighted MRI, and MRS can be used to evaluate the severity of neonatal asphyxia.

METHODS

Twenty infants with 1-minute Apgar scores of 6 or less were studied at 2 to 28 days of age. The MRS variables were compared with routine and diffusion-weighted brain MRI. Clinical variables and MRS findings were subjected to factor analysis and stepwise multiple regressions to determine interrelationships.

RESULTS

The BG region NAA-Cho and NAA-ChoCr ratios correlated with the 1-minute (P<.001) and 5-minute (P = .01 for NAA-Cho; P = .006 for NAA-ChoCr). There was no correlation between metabolite levels and the 10-minute Apgar scores. The stongest predictions exist between the 1-minute Apgar scores and the NAA-Cho and NAA-ChoCr ratios. In the anterior border zone, the only correlation was between the 1-minute Apgar score and the NAA-Cho ratio, but there was a strong age effect in these data. Lactate was found in the BG of 3 infants, all of whom had 5-minute Apgar scores of 6 or less. Three patients had focal lesions on MRI; 2 of these had elevated lactate levels in the abnormal region; and the third, who had an intrauterine stroke, had no lactate in the region.

CONCLUSIONS

Correlations between NAA-Cho and NAA-ChoCr ratios and the 1- and 5-minute Apgar scores are stronger in the BG region than in the frontal border zone. The presence or absence of lactate may indicate the severity of the brain insult, and the combination of MRS, MRI, and diffusion-weighted MRI may assist in localizing and predicting a long-term brain injury.

A light and electron microscopic study of GAT-1 in the monkey basal ganglia

The distribution of the GABA transporter GAT-1 was studied by immunocytochemistry and electron microscopy in the monkey basal ganglia. Dense staining was observed in the globus pallidus externa and interna, intermediate in the subthalamic nucleus, and substantia nigra, and light staining in the caudate nucleus and putamen. Staining was observed in axon terminals, but not cell bodies. Electron microscopy showed that the GAT-1 positive axon terminals formed symmetrical synapses, suggesting that they were the terminals of GABAergic neurons. Comparison of areas high in GAT-1 protein with that of GABA showed a good correlation between the density in neuropil staining for GAT-1, and that of GABA.

Differential regulation of tyrosine hydroxylase in the basal ganglia of mice lacking the dopamine transporter

Mice lacking the dopamine transporter (DAT) display biochemical and behavioural dopaminergic hyperactivity despite dramatic alteration in dopamine homeostasis. In order to determine the anatomical and functional integrity of the dopaminergic system, we examined the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of dopamine synthesis as well as DOPA decarboxylase and vesicular monoamine transporter. TH-positive neurons in the substantia nigra were only slightly decreased (-27.6 +/- 4.5%), which can not account for the dramatic decreases in the levels of TH and dopamine that we previously observed in the striatum. TH mRNA levels were decreased by 25% in the ventral midbrain with no modification in the ratio of TH mRNA levels per cell. However, TH protein levels were decreased by 90% in the striatum and 35% in the ventral midbrain. In the striatum, many dopaminergic projections had no detectable TH, while few projections maintained regular labelling as demonstrated using electron microscopy. DOPA decarboxylase levels were not modified and vesicular transporter levels were decreased by only 28.7% which suggests that the loss of TH labelling in the striatum is not due to loss of TH projections. Interestingly, we also observed sporadic TH-positive cell bodies using immunohistochemistry and in situ hybridization in the striatum of homozygote mice, and to some extent that of wild-type animals, which raises interesting possibilities as to their potential contribution to the dopamine hyperactivity and volume transmission previously reported in these animals. In conjunction with our previous findings, these results highlight the complex regulatory mechanisms controlling TH expression at the level of mRNA, protein, activity and distribution. The paradoxical hyperdopaminergia in the DAT KO mice despite a marked decrease in TH and dopamine levels suggests a parallel to Parkinson's disease implying that blockade of DAT may be beneficial in this condition.

Compounds containing cytosolic choline in the basal ganglia: a potential biological marker of true drug response to fluoxetine

OBJECTIVE

Studies have identified two types of antidepressant response: true drug response and placebo pattern response. This study examined the relationship between true drug response and choline-creatine ratios in the basal ganglia of depressed patients treated with fluoxetine.

METHOD

The authors evaluated drug-free outpatients with major depression before (N = 41) and after (N = 15) 8 weeks of fluoxetine treatment, 20 mg/day, by using proton magnetic resonance spectroscopy.

RESULTS

There was a significant difference in the degree of change from baseline to week 8 in choline-creatine ratios between the true drug response group (N = 8) and the placebo pattern response/nonresponse group (N = 7); the true drug response patients had a 20% increase in choline-creatine ratios, and the placebo pattern response/nonresponse patients had a 12% decrease in choline-creatine ratios.

CONCLUSIONS

These data suggest that true drug response to fluoxetine treatment in depression may be associated with an increase in choline-creatine ratios in the basal ganglia.

Effect of a functional impairment of corticostriatal transmission on cortically evoked expression of c-Fos and zif 268 in the rat basal ganglia

The activity-dependent induction of immediate-early genes is commonly used to map activated neuronal networks. In a previous analysis of the cortico-basal ganglia circuits, we have shown that a cortical stimulation produces Fos protein expression in the striatum and the subthalamic nucleus, with a pattern which conforms to the anatomical organization of cortical projections [Sgambato V. et al. (1996) Neuroscience 81, 93-112]. In the present study, we examined the effects of a unilateral blockade of the corticostriatal transmission on c-fos and zif 268 messenger RNA expression evoked in the substantia nigra pars reticulata and the subthalamic nucleus following stimulation of the ipsilateral motor cortex. The blockade of the corticostriatal pathway was performed either by an excitotoxic striatal lesion or by an application of the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione within the striatum. After application of the glutamate receptor antagonist, which prevented the cortical stimulation activating the GABAergic striatonigral pathway, the induction of both c-fos and zif 268 messenger RNAs was facilitated in the ipsilateral substantia nigra pars reticulata. In the subthalamic nucleus ipsilateral to the application of 6-cyano7-nitroquinoxaline-2,3-dione, the cellular discharges evoked by stimulation of the cortex were considerably shortened as a result of the blockade of the disinhibitory striato-pallido-subthalamic circuit. However, a strong expression of immediate-early genes was still induced by the cortical stimulation. By contrast, after unilateral kainate lesion of the striatum, the cortical stimulation was no longer able to induce c-fos and zif 268 messenger RNA expression in the ipsilateral subthalamic nucleus and in the substantia nigra pars reticulata bilaterally. The lack of immediate-early gene induction strongly contrasted with the neuronal discharges evoked in these nuclei by the cortical stimulation. Comparison between the cortically evoked neuronal activities and the pattern of immediate-early gene expression suggests that the induction of immediate-early genes in the basal ganglia mainly reflects the level of synaptic activity rather than the frequency of discharge of the postsynaptic neurons. Moreover, the results stress that modifications of immediate-early gene expression observed in the basal ganglia after an acute or a chronic interruption of the corticostriatal transmission are not superimposable.

Distribution and properties of GABA(B) antagonist [3H]CGP 62349 binding in the rhesus monkey thalamus and basal ganglia and the influence of lesions in the reticular thalamic nucleus

GABA(B) receptors are believed to be associated with the efferents of the nucleus reticularis thalami, which is implicated in the regulation of activity in the thalamocortical-corticothalamic circuit and plays a role in absence seizures. Yet, the distribution of GABA(B) receptors in the thalamus has only been studied in the rat, and there is no comparable information in primates. The potent GABA(B) receptor antagonist [3H]CGP 62349 was used to study the distribution and binding properties of the receptor in control monkeys and those with small ibotenic acid lesions in the anterodorsal segment of the nucleus reticularis thalami. Eight-micrometer-thick cryostat sections of the fresh frozen brains were incubated in the presence of varying concentrations of the ligand. Autoradiographs were analysed using a quantitative image analysis technique, and binding parameters were calculated for select thalamic nuclei as well as basal ganglia structures present in the same sections. The overall number of GABA(B) binding sites in the monkey thalamus and basal ganglia was several-fold higher than previously reported values for the rat. In the thalamus, the receptors were distributed rather uniformly and the binding densities and affinities were high (Bmax range of 245.5-437.9 fmol/ mg of tissue, Kd range of 0.136-0.604 nM). In the basal ganglia, the number of binding sites and the affinities were lower (Bmax range of 51.1-244.2 fmol/mg of tissue; K(d) range of 0.416-1.394 nM), and the differences between nuclei were more pronounced, with striatum and substantia nigra pars compacta displaying the highest binding densities. Seven days post-lesion, a 20-30% decrease in Bmax values (P < 0.05) was found in the nuclei receiving input from the lesioned nucleus reticularis thalami sector (the mediodorsal nucleus and densicellular and magnocellular parts of the ventral anterior nucleus) without changes in affinity. No significant changes were detected in any other structures. The results of the lesioning experiments suggest that a portion of thalamic GABA(B) receptors is in a presynaptic location on the nucleus reticularis thalami efferents. The overall distribution pattern in the thalamus also suggests a partial association of GABA(B) receptors with corticothalamic terminals presynaptically.