101 research outputs found
Relationships between thalamostriatal neurons and pedunculopontine projections to the thalamus: a neuroanatomical tract-tracing study in the rat
Detection of cannabinoid receptors CB1 and CB2 within basal ganglia output neurons in macaques: changes following experimental parkinsonism
Abstract Although type 1 cannabinoid receptors (CB1-
Rs) are expressed abundantly throughout the brain, the
presence of type 2 cannabinoid receptors (CB2Rs) in neurons
is still somewhat controversial. Taking advantage of
newly designed CB1R and CB2R mRNA riboprobes, we
demonstrate by PCR and in situ hybridization that transcripts
for both cannabinoid receptors are present within
labeled pallidothalamic-projecting neurons of control and
MPTP-treated macaques, whereas the expression is markedly
reduced in dyskinetic animals. Moreover, an in situ
proximity ligation assay was used to qualitatively assess
the presence of CB1Rs and CB2Rs, as well as CB1RâCB2R
heteromers within basal ganglia output neurons in all
animal groups (control, parkinsonian and dyskinetic
macaques). A marked reduction in the number of CB1Rs,
CB2Rs and CB1RâCB2R heteromers was found in dyskinetic
animals, mimicking the observed reduction in CB1R
and CB2R mRNA expression levels. The fact that chronic
levodopa treatment disrupted CB1RâCB2R heteromeric
complexes should be taken into consideration when
designing new drugs acting on cannabinoid receptor
heteromers
Glucocerebrosidase expression patterns in the non-human primate brain
Glucocerebrosidase (GCase) is a lysosomal
enzyme encoded by the GBA1 gene. Mutations in GBA1
gene lead to Gaucherâs disease, the most prevalent lysosomal storage disorder. GBA1 mutations reduce GCase
activity, therefore promoting the aggregation of alphasynuclein, a common neuropathological finding underlying
Parkinsonâs disease (PD) and dementia with Lewy bodies.
However, it is also worth noting that a direct link between
GBA1 mutations and alpha-synuclein aggregation indicating cause and effect is still lacking, with limited experimental evidence to date. Bearing in mind that a number of
strategies increasing GCase expression for the treatment of
PD are currently under development, here we sought to
analyze the baseline expression of GCase in the brain of
Macaca fascicularis, which has often been considered as
the gold-standard animal model of PD. Although as with
other lysosomal enzymes, GCase is expected to be ubiquitously expressed, here a number of regional variations
have been consistently found, together with several specific
neurochemical phenotypes expressing very high levels of
GCase. In this regard, the most enriched expression of
GCase was constantly found in cholinergic neurons from
the nucleus basalis of Meynert, dopaminergic cells in the
substantia nigra pars compacta, serotoninergic neurons
from the raphe nuclei, as well as in noradrenergic neurons
located in the locus ceruleus. Moreover, it is also worth
noting that moderate levels of expression were also found
in a number of areas within the paleocortex and archicortex, such as the entorhinal cortex and the hippocampal
formation, respectively
Long-Distance Three-Color Neuronal Tracing in Fixed Tissue Using NeuroVue Dyes
Dissecting development of neuronal connections is critical for understanding neuronal function in both normal and diseased states. Charting the development of the multitude of connections is a monumental task, since a given neuron typically receives hundreds of convergent inputs from other neurons and provides divergent outputs for hundreds of other neurons. Although progress is being made utilizing various mutants and/or genetic constructs expressing fluorescent proteins like GFP, substantial work remains before a database documenting the development and final location of the neuronal pathways in an adult animal is completed. The vast majority of developing neurons cannot be specifically labeled with antibodies and making specific GFP-expressing constructs to tag each of them is an overwhelming task. Fortunately, fluorescent lipophilic dyes have emerged as very useful tools to systematically compare changes in neuronal networks between wild-type and mutant mice. These dyes diffuse laterally along nerve cell membranes in fixed preparations, allowing tracing of the position of a given neuron within the neuronal network in murine mutants fixed at various stages of development. Until recently, however, most evaluations have been limited to one, or at most, two color analyses. We have previously reported three color neuronal profiling using the novel lipophilic dyes NeuroVue (NV) Green, Red and Maroon (Fritzsch et al., Brain. Res. Bull. 66:249â258, 2005). Unfortunately such three color experiments have been limited by the fact that NV Green and its brighter successor, NV Emerald, both exhibit substantially decreased signal intensities when times greater than 48 hours at 37°C are required to achieve neuronal profile filling (unpublished observations). Here we describe a standardized test system developed to allow comparison of candidate dyes and its use to evaluate a series of 488 nm-excited green-emitting lipophilic dyes. The best of these, NV Jade, has spectral properties well matched to NV Red and NV Maroon, better solubility in DMF than DiO or DiA, improved thermostability compared with NV Emerald, and the ability to fill neuronal profiles at rates of 1 mm per day for periods of at least 5 days. Use of NV Jade in combination with NV Red and NV Maroon substantially improves the efficiency of connectional analysis in complex mutants and transgenic models where limited numbers of specimens are available
The basal ganglia and thalamus of the long-tailed macaque in stereotaxic coordinates. A template atlas based on coronal, sagittal and horizontal brain sections
A stereotaxic brain atlas of the basal ganglia and thalamus of Macaca fascicularis presented here is designed with a surgical perspective. In this regard, all coordinates have been referenced to a line linking the anterior and posterior commissures (acâpc line) and considering the center of the ac at the midline as the origin of the bicommissural space. The atlas comprises of 43 different plates (19 coronal levels, 10 sagittal levels and 14 horizontal levels). In addition to âclassicalâ cyto- and chemoarchitectural techniques such as the Nissl method and the acetylcholinesterase stain, several immunohistochemical stains have been performed in adjacent sections, including the detection of tyrosine hydroxylase, enkephalin, neurofilaments, parvalbumin and calbindin. In comparison to other existing stereotaxic atlases for M. fasicularis, this atlas has two main advantages: firstly, brain cartography is based on a wide variety of cyto- and chemoarchitectural stains carried out on adjacent sections, therefore enabling accurate segmentation. Secondly and most importantly, sagittal and horizontal planes are included. Sagittal planes are very useful for calculating oblique trajectories, whereas, clinical researchers engaged in neuroimaging studies will be more familiar with horizontal sections, as they use horizontal (also called âaxialâ) brain images in their daily routine of their clinical practices
A proposal for a coordinated effort for the determination of brainwide neuroanatomical connectivity in model organisms at a mesoscopic scale
In this era of complete genomes, our knowledge of neuroanatomical circuitry
remains surprisingly sparse. Such knowledge is however critical both for basic
and clinical research into brain function. Here we advocate for a concerted
effort to fill this gap, through systematic, experimental mapping of neural
circuits at a mesoscopic scale of resolution suitable for comprehensive,
brain-wide coverage, using injections of tracers or viral vectors. We detail
the scientific and medical rationale and briefly review existing knowledge and
experimental techniques. We define a set of desiderata, including brain-wide
coverage; validated and extensible experimental techniques suitable for
standardization and automation; centralized, open access data repository;
compatibility with existing resources, and tractability with current
informatics technology. We discuss a hypothetical but tractable plan for mouse,
additional efforts for the macaque, and technique development for human. We
estimate that the mouse connectivity project could be completed within five
years with a comparatively modest budget.Comment: 41 page
Calbindin content and differential vulnerability of midbrain efferent dopaminergic neurons in macaques
Calbindin (CB) is a calcium binding protein reported to protect dopaminergic neurons from
degeneration. Although a direct link between CB content and differential vulnerability of
dopaminergic neurons has long been accepted, factors other than CB have also been
suggested, particularly those related to the dopamine transporter. Indeed, several studies
have reported that CB levels are not causally related to the differential vulnerability
of dopaminergic neurons against neurotoxins. Here we have used dual stains for
tyrosine hydroxylase (TH) and CB in 3 control and 3 MPTP-treated monkeys to visualize
dopaminergic neurons in the ventral tegmental area (VTA) and in the dorsal and ventral
tiers of the substantia nigra pars compacta (SNcd and SNcv) co-expressing TH and CB.
In control animals, the highest percentages of co-localization were found in VTA (58.2%),
followed by neurons located in the SNcd (34.7%). As expected, SNcv neurons lacked CB
expression. In MPTP-treated animals, the percentage of CB-ir/TH-ir neurons in the VTA
was similar to control monkeys (62.1%), whereas most of the few surviving neurons in
the SNcd were CB-ir/TH-ir (88.6%). Next, we have elucidated the presence of CB within
identified nigrostriatal and nigroextrastriatal midbrain dopaminergic projection neurons. For
this purpose, two control monkeys received one injection of Fluoro-Gold into the caudate
nucleus and one injection of cholera toxin (CTB) into the postcommissural putamen,
whereas two more monkeys were injected with CTB into the internal division of the globus
pallidus (GPi). As expected, all the nigrocaudate- and nigroputamen-projecting neurons
were TH-ir, although surprisingly, all of these nigrostriatal-projecting neurons were negative
for CB. Furthermore, all the nigropallidal-projecting neurons co-expressed both TH and
CB. In summary, although CB-ir dopaminergic neurons seem to be less prone to MPTPinduced
degeneration, our data clearly demonstrated that these neurons are not giving rise
to nigrostriatal projections and indeed CB-ir/TH-ir neurons only originate nigroextrastriatal
projections
Adeno-associated viral vectors serotype 8 for cell-specific delivery of therapeutic genes in the central nervous system
Adeno-associated viruses (AAVs) have become highly promising tools for research and clinical applications in the central nervous system (CNS). However, specific delivery of genes to the cell type of interest is essential for the success of gene therapy and therefore a correct selection of the promoter plays a very important role. Here, AAV8 vectors carrying enhanced green fluorescent protein (eGFP) as reporter gene under the transcriptional control of different CNS-specific promoters were used and compared with a strong ubiquitous promoter. Since one of the main limitations of AAV-mediated gene delivery lies in its restricted cloning capacity, we focused our work on small-sized promoters. We tested the transduction efficacy and specificity of each vector after stereotactic injection into the mouse striatum. Three glia-specific AAV vectors were generated using two truncated forms of the human promoter for glial fibrillar acidic protein (GFAP) as well as a truncated form of the murine GFAP promoter. All three vectors resulted in predominantly glial expression; however we also observed eGFP expression in other cell-types such as oligodendrocytes, but never in neurons. In addition, robust and neuron-specific eGFP expression was observed using the minimal promoters for the neural protein BM88 and the neuronal nicotinic receptor ÎČ2 (CHRNB2). In summary, we developed a set of AAV vectors designed for specific expression in cells of the CNS using minimal promoters to drive gene expression when the size of the therapeutic gene matters
Two Affinity Sites of the Cannabinoid Subtype 2 Receptor Identified by a Novel Homogeneous Binding Assay
Goal-directed and habitual control in the basal ganglia: implications for Parkinson's disease
Progressive loss of the ascending dopaminergic projection in the basal ganglia is a fundamental pathological feature of Parkinson's disease. Studies in animals and humans have identified spatially segregated functional territories in the basal ganglia for the control of goal-directed and habitual actions. In patients with Parkinson's disease the loss of dopamine is predominantly in the posterior putamen, a region of the basal ganglia associated with the control of habitual behaviour. These patients may therefore be forced into a progressive reliance on the goal-directed mode of action control that is mediated by comparatively preserved processing in the rostromedial striatum. Thus, many of their behavioural difficulties may reflect a loss of normal automatic control owing to distorting output signals from habitual control circuits, which impede the expression of goal-directed action. © 2010 Macmillan Publishers Limited. All rights reserved
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