Whole-brain Sections Research Articles

Micron-resolution fiber mapping in histology independent of sample preparation.

Detailed knowledge of the brain's nerve fiber network is crucial for understanding its function in health and disease. However, mapping fibers with high resolution remains prohibitive in most histological sections because state-of-the-art techniques are incompatible with their preparation. Here, we present a micron-resolution light-scattering-based technique that reveals intricate fiber networks independent of sample preparation for extended fields of view. We uncover fiber structures in both label-free and stained, paraffin-embedded and deparaffinized, newly-prepared and archived, animal and human brain tissues - including whole-brain sections from the BigBrain atlas. We identify altered microstructures in demyelination and hippocampal neurodegeneration, and show key advantages over diffusion magnetic resonance imaging, polarization microscopy, and structure tensor analysis. We also reveal structures in non-brain tissues - including muscle, bone, and blood vessels. Our cost-effective, versatile technique enables studies of intricate fiber networks in any type of histological tissue section, offering a new dimension to neuroscientific and biomedical research.

Neuronal circuits sustaining neocortical-injury-induced status epilepticus

ObjectivesAcute injuries or insults to the cortex, such as trauma, subarachnoid hemorrhage, lobar hemorrhage, can cause seizures or status epilepticus(SE). Neocortical SE is associated with coma, worse prognosis, delayed recovery, and the development of epilepsy. The anatomical structures progressively recruited during neocortical-onset status epilepticus (SE) is unknown. Therefore, we constructed large-scale maps of brain regions active during neocortical SE. MethodsWe used a neocortical injury-induced SE mouse model. We implanted cobalt (Co) in the right supplementary motor cortex (M2). We 16 h later administered a homocysteine injection (845 mg/kg, intraperitoneal) to C57Bl/6 J mice to induce SE and monitored it by video and EEG. We harvested animals for 1 h (early-stage) and 2 h (late-stage) following homocysteine injections. To construct activation maps, we immunolabeled whole-brain sections for cFos and NeuN, imaged them using a confocal microscope and quantified cFos immunoreactivity (IR). ResultsSE in the early phase consisted of discrete, focal intermittent seizures, which became continuous and bilateral in the late stage. In this early stage, cFos IR was primarily observed in the right hemisphere, ipsilateral to the Co lesion, specifically in the motor cortex, retrosplenial cortex, somatosensory cortex, anterior cingulate cortex, lateral and medial septal nuclei, and amygdala. We observed bilateral cFos IR in brain regions during the late stage, indicating the bilateral spread of focal seizures. We found increased cFOS IR in the bilateral somatosensory cortex and the motor cortex and subcortical regions, including the amygdala, thalamus, and hypothalamus. There was noticeably different, intense cFos IR in the bilateral hippocampus compared to the early stage. In addition, there was higher activity in the cortex ipsilateral to the seizure focus during the late stage compared with the early one. ConclusionWe present a large-scale, high-resolution map of seizure spread during neocortical injury-induced SE. Cortico-cortical and cortico subcortical re-entrant circuits sustain neocortical SE. Neuronal loss following neocortical SE, distant from the neocortical focus, may result from seizures.

An Automated Approach to Improve the Quantification of Pericytes and Microglia in Whole Mouse Brain Sections.

Whole slide scanning technology has enabled the generation of high-resolution images from complete tissue sections. However, commonly used analysis software is often unable to handle the large data files produced. Here, we present a method using the open-source software QuPath to detect, classify and quantify fluorescently-labeled cells (microglia and pericytes) in whole coronal brain tissue sections. Whole-brain sections from both male and female NG2DsRed x CX3CR1+/GFP mice were analyzed. Small regions of interest were selected and manual counts were compared with counts generated from an automated approach, across a range of detection parameters. The optimal parameters for detecting cells and classifying them as microglia or pericytes in each brain region were determined and applied to annotations corresponding to the entire somatosensory and motor cortices, hippocampus, thalamus, and hypothalamus in each section. 3.74% of all detected cells were classified as pericytes; however, this proportion was significantly higher in the thalamus (6.20%) than in other regions. In contrast, microglia (4.51% of total cells) were more abundant in the cortex (5.54%). No differences were detected between male and female mice. In conclusion, QuPath offers a user-friendly solution to whole-slide image analysis which could lead to important new discoveries in both health and disease.

Convolutional neural networks for cytoarchitectonic brain mapping at large scale

Human brain atlases provide spatial reference systems for data characterizing brain organization at different levels, coming from different brains. Cytoarchitecture is a basic principle of the microstructural organization of the brain, as regional differences in the arrangement and composition of neuronal cells are indicators of changes in connectivity and function. Automated scanning procedures and observer-independent methods are prerequisites to reliably identify cytoarchitectonic areas, and to achieve reproducible models of brain segregation. Time becomes a key factor when moving from the analysis of single regions of interest towards high-throughput scanning of large series of whole-brain sections. Here we present a new workflow for mapping cytoarchitectonic areas in large series of cell-body stained histological sections of human postmortem brains. It is based on a Deep Convolutional Neural Network (CNN), which is trained on a pair of section images with annotations, with a large number of un-annotated sections in between. The model learns to create all missing annotations in between with high accuracy, and faster than our previous workflow based on observer-independent mapping. The new workflow does not require preceding 3D-reconstruction of sections, and is robust against histological artefacts. It processes large data sets with sizes in the order of multiple Terabytes efficiently. The workflow was integrated into a web interface, to allow access without expertise in deep learning and batch computing. Applying deep neural networks for cytoarchitectonic mapping opens new perspectives to enable high-resolution models of brain areas, introducing CNNs to identify borders of brain areas.

Quantitative birefringence microscopy for imaging the structural integrity of CNS myelin following circumscribed cortical injury in the rhesus monkey.

Significance: Myelin breakdown is likely a key factor in the loss of cognitive and motor function associated with many neurodegenerative diseases.Aim: New methods for imaging myelin structure are needed to characterize and quantify the degradation of myelin in standard whole-brain sections of nonhuman primates and in human brain.Approach: Quantitative birefringence microscopy (qBRM) is a label-free technique for rapid histopathological assessment of myelin structural breakdown following cortical injury in rhesus monkeys.Results: We validate birefringence microscopy for structural imaging of myelin in rhesus monkey brain sections, and we demonstrate the power of qBRM by characterizing the breakdown of myelin following cortical injury, as a model of stroke, in the motor cortex.Conclusions: Birefringence microscopy is a valuable tool for histopathology of myelin and for quantitative assessment of myelin structure. Compared to conventional methods, this label-free technique is sensitive to subtle changes in myelin structure, is fast, and enables more quantitative assessment, without the variability inherent in labeling procedures such as immunohistochemistry.

Mass spectrometry imaging of blast overpressure induced modulation of GABA/glutamate levels in the central auditory neuraxis of Chinchilla

Acoustic trauma damages inner ear neural structures including cochlear hair cells which result in hearing loss and neurotransmitter imbalances within the synapses of the central auditory pathway. Disruption of GABA/glutamate levels underlies, tinnitus, a phantom perception of sound that persists post-exposure to blast noise which may manifest in tandem with acute/chronic loss of hearing. Many putative theories explain tinnitus physiology based on indirect and direct assays in animal models and humans, although there is no comprehensive evidence to explain the phenomenon. Here, GABA/glutamate levels were imaged and quantified in a blast overpressure model of chinchillas using Fourier transform ion cyclotron resonance mass spectrometry imaging. The direct measurement from whole-brain sections identified the relative levels of GABA/glutamate in the central auditory neuraxis centers including the cochlear nucleus, inferior colliculus, and auditory cortex. These preliminary results provide insight on the homeostasis of GABA/glutamate within whole-brain sections of chinchilla for investigation of the pathomechanism of blast-induced tinnitus.

Histological Correlates of Diffusion-Weighted Magnetic Resonance Microscopy in a Mouse Model of Mesial Temporal Lobe Epilepsy.

Mesial temporal lobe epilepsy (MTLE) is the most common type of focal epilepsy. It is frequently associated with abnormal MRI findings, which are caused by underlying cellular, structural, and chemical changes at the micro-scale. In the current study, it is investigated to which extent these alterations correspond to imaging features detected by high resolution magnetic resonance imaging in the intrahippocampal kainate mouse model of MTLE. Fixed hippocampal and whole-brain sections of mouse brain tissue from nine animals under physiological and chronically epileptic conditions were examined using structural and diffusion-weighted MRI. Microstructural details were investigated based on a direct comparison with immunohistochemical analyses of the same specimen. Within the hippocampal formation, diffusion streamlines could be visualized corresponding to dendrites of CA1 pyramidal cells and granule cells, as well as mossy fibers and Schaffer collaterals. Statistically significant changes in diffusivities, fractional anisotropy, and diffusion orientations could be detected in tissue samples from chronically epileptic animals compared to healthy controls, corresponding to microstructural alterations (degeneration of pyramidal cells, dispersion of the granule cell layer, and sprouting of mossy fibers). The diffusion parameters were significantly correlated with histologically determined cell densities. These findings demonstrate that high-resolution diffusion-weighted MRI can resolve subtle microstructural changes in epileptic hippocampal tissue corresponding to histopathological features in MTLE.

Automated Quantification of Immunohistochemical Staining of Large Animal Brain Tissue Using QuPath Software

Large scale unbiased quantification of immunohistochemistry (IHC) is time consuming, expensive, and/or limited in scope. Heterogeneous tissue types such as brain tissue have presented a further challenge to the development of automated analysis, as differing cellular morphologies result in either limited applicability or require large amounts of training tissue for machine-learning methods. Here we present the use of QuPath, a free and open source software, to quantify whole-brain sections stained with the immunohistochemical markers IBA1 and AT8, for microglia and phosphorylated tau respectively. The pixel-based method of analysis herein allows for statistical comparison of global protein expression between brains and generates heat-maps of stain intensity, visualizing stain signal across whole sections and permitting more specific investigation of regions of interest. This method is fast, automated, unbiased, and easily replicable. We compared swine brains that had undergone a closed head traumatic brain injury with brains of sham animals, and found a global increase in both microglial signal expression and phosphorylated tau. We discuss the IHC methods necessary to utilize this analysis and provide detailed instruction on the use of QuPath in the pixel-based analysis of whole-slide images.

Reduced volumes of the external and internal globus pallidus in male heroin addicts: a postmortem study.

Deep brain stimulation (DBS) of the globus pallidus internus was recently proposed as a potential new treatment target for opioid addiction. DBS requires computer-assisted-3D planning to implant the stimulation electrode precisely. As volumes of brain regions may differ in addiction compared to healthy controls, our aim was to investigate possible volume differences in addicts compared to healthy controls. Volumes of the globus pallidus externus (PE) and internus (PI) in heroin addicts (n = 14) and healthy controls (n = 12) were assessed using morphometry of serial whole-brain sections. Total brain volume was larger in the heroin group (mean 1479 ± 62cm3 vs. mean 1352 ± 103cm3), as the heroin group was more than 10years younger (p = 0.001). Despite larger mean whole brain volume, the mean relative volume of the PE and PI was smaller in addicted subjects compared to healthy controls (PE 0.658 ± 0.183 × 10-3 vs. 0.901 ± 0.284 × 10-3; ANOVA F(1, 24) = 6.945, p = 0.014, η2 = 0.224; PI 0.253 ± 0.095 × 10-3 vs. 0.345 ± 0.107 × 10-3; ANOVA F(1, 24) = 5.374, p = 0.029, η2 = 0.183). These findings were not significantly confounded by age, duration of autolysis, and fixation time. Our results provide further evidence for structural and not only functional deficits of the globus pallidus in addiction. In the context of previous studies, our findings support the idea of shared pathophysiological processes between comorbid depression and impulsivity in opioid addiction.

Decoding the microstructural correlate of diffusion MRI.

Diffusion imaging has evolved considerably over the past decade. While it provides valuable information about the structural connectivity at the macro- and mesoscopic scale, bridging the gap to the microstructure at the level of single nerve fibers poses an enormous challenge. This is particularly true for the human brain with its large size, its large white-matter volume and availability of histological techniques for studying human whole-brain sections and subsequent 3D reconstruction. Classic post-mortem techniques for studying the fiber architecture of the brain, such as myeloarchitectonic staining or dye tracing, are complemented by novel histological approaches, such as 3D polarized light imaging or optical coherence tomography, enabling unique insight into the fiber architecture from large fiber bundles within deep white matter to single nerve fibers in the cortex. The present review discusses the benefits and challenges of these latest developments in comparison with the classic techniques, with particular focus on the mutual exchange between in vivo and post-mortem diffusion imaging and post-mortem microstructural approaches for understanding the wiring of the brain across different scales.

Total hypothalamic volume is reduced in postmortem brains of male heroin addicts

The hypothalamus is at the core of the stress responses systems of the brain. Most interestingly, even though changes of HPA-function have been observed in opiate addiction not much is known about structural changes of the hypothalamus. Volumes of hypothalamus in heroin addicts (n=14) and healthy controls (n=12) were assessed by using morphometry of serial whole-brain sections. Total brain volume was larger in the heroin group (mean 1478.85±62.34cm3 vs. mean 1352.38±103.24cm3), as the heroin group was more than 10years younger (p=0.001). Thus, diagnosis-related effects in the hypothalamus were assessed using the hypothalamus volume relative to whole brain volume showing reduced volumes of the hypothalamus in the heroin group (0.201±0.074×10-3 vs. 0.267±0.048×10-3; ANOVA: F(1,23)=6.211, p=0.020) with a strong hemispheric effect (left side: about 20% reduction 0.209±0.080×10-3 vs. 0.264±0.049×10-3; F=4.109; p=0.054; right side: about 27% reduction, 0.198±0.069×10-3 vs. 0.271±0.050×10-3; F=-8.800; p=0.007). Our results provide further evidence for structural and not only functional deficits of the hypothalamus in addiction.

Distribution of Tyrosine hydroxylase immunoreactivity in the CNS of the common carp Cyprinus carpio

Catecholamines, including dopamine, are the principal neurotransmitters mediating a variety of functions in the CNS, such as motor control, cognition, emotion, memory processing, and endocrine modulation. Dysfunctional catecholamine neurotransmission is also implicated in neurologic and neuropsychiatric disorders. Human brain diseases, such as Parkinson’s disease (1), have been recently approached by using fish models, especially cyprinid teleosts, given basic similarities of the fish brain to that of mammals. The distribution of the catecholaminergic system has been studied in the forebrain of several teleosts, but relevant information are not available for the common carp, Cyprinus carpio, which is a model species in several studies. In this study, we have analyzed the distribution of catecholaminergic neurons in the carp brain by immunohistochemistry using a specific antibody to tyrosine hydroxylase (TH) on transverse serial frozen sections of the whole brain. In the carp brain, TH-immunoreactive (ir) neurons were present in several nuclei. In particular, positive neurons were detected in the ventral nucleus of the ventral telencephalic area. In addition, neuronal bodies and varicose fibers were stained for TH in the preoptic region, from the anterior to the posterior nuclei, in the suprachiasmatic nucleus, in the ventrolateral and ventromedial talamic nuclei. Moreover TH-ir neurons were also distributed in the periventricular pretectum and locus coeruleus. TH-ir structures were localized not only in recognizable catecholaminergic nuclei, corresponding to those of mammalian brain, but also in regions that are uniquely organized in teleosts, including the ventral telencephalon, the anterior and posterior preoptic region, the ventromedial thalamus, suggesting that they may be useful in elucidating homologies between fish and mammal brain. The present study partially confirmed TH distribution in other CNS of cyprinids (2), and provided more detailed information to a better understanding of the evolution of catecholaminergic system in vertebrates.

Postmortem volumetric analysis of the nucleus accumbens in male heroin addicts: implications for deep brain stimulation.

Deep brain stimulation (DBS) of the nucleus accumbens (NAc) is increasingly investigated in neuropsychiatric disorders. DBS requires computer-assisted 3D planning to implant the stimulation electrode precisely. Recently, there has been a debate about the true dimensions of NAc in healthy as well as in mentally ill individuals. Knowing its true dimensions in different neuropsychiatric disorders may improve even more precise targeting of NAc for therapeutic DBS. Volumes of NAc of heroin addicts (n = 14) and healthy controls (n = 12) were calculated by using morphometry of serial whole-brain sections. Total brain volume was larger in the heroin group (mean 1478.85 ± 62.34 vs. mean 1352.38 ± 103.24 cm(3)), as the heroin group was more than 10 years younger (p = 0.001). However, the mean volume of the NAc in heroin addicts was smaller than in controls (0.528 ± 0.166 vs. 0.623 ± 0.196 cm(3); p = 0.019). This group effect did not significantly differ between the hemispheres. When assessed separately, left-hemispheric NAc volume was 15 % lower (p = 0.020), while right-hemispheric NAc volume was 16 % lower (p = 0.047) in the heroin-addicted group compared to controls. Based on these diagnosis-related differences, we believe it is important to further analyze NAc volumes in different psychiatric disorders to further improve precise targeting and electrode placement.

Febrile Infection-Related Epilepsy Syndrome without Detectable Autoantibodies and Response to Immunotherapy: A Case Series and Discussion of Epileptogenesis in FIRES

Febrile infection-related epilepsy syndrome (FIRES) is a severe postinfectious epileptic encephalopathy in previously healthy children and has three phases: the initial phase with a simple febrile infection, a few days later the acute phase characterized by a peracute onset of highly recurrent seizures or refractory status epilepticus often with no more fever and generally without additional neurological features (the classical pure seizure phenotype), and last, the chronic phase with a drug-resistant epilepsy and neuropsychological impairments. FIRES seems to be sporadic and very rare: we estimated the annual incidence in children and adolescents by a prospective hospital-based German-wide surveillance as 1 in 1,000,000. Because of the preceding infection and lacking evidence of infectious encephalitis, an immune-mediated pathomechanism and, therefore, a response to immunotherapies may be involved. To test the hypothesis that antibodies against neuronal structures cause FIRES, we analyzed sera of 12 patients aged 2 to 12 years (median 6 years) and cerebral spinal fluids (CSFs) of 3 of these 12 patients with acute or chronic FIRES. We studied six patients (two including CSF) 1 to 14 weeks (median 3 weeks) and six patients 1 to 6 years (median 3.5 years) after seizure onset. All samples were analyzed for antibodies against glutamate receptors of type N-methyl-D-aspartate (NMDA) and type α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA), gamma-aminobutyric acid (GABA)B-receptors, voltage-gated potassium channel (VGKC)-associated proteins leucin-rich glioma inactivated 1 (LGI1) and contactin-associated protein like 2 (CASPR2), and glutamic acid decarboxylase (GAD) by a multiparametric recombinant immunofluorescence assay employing human embryonic kidney (HEK) cells transfected with cDNAs for the antigens. In addition, indirect immunohistochemistry using rat whole-brain sections was done in three patients. Finally, sera of 10 patients were tested for VGKC complex antibodies by radioimmunoprecipitation assay (RIA). None of the antibody tests were positive in any of the patients. Moreover, steroids, immunoglobulins, and plasmapheresis had no clear effect in the seven patients receiving immunotherapy. The failure of antibody-detection against the known neuronal antigens as well as the ineffectiveness of immunotherapy questions a role for autoantibodies in the epileptogenesis of classical FIRES. As we discuss, other underlying causes need to be considered including the possibility of a mitochondrial encephalopathy.

The importance of combining MRI and large-scale digital histology in neuroimaging studies of brain connectivity and disease.

One of the major issues hindering a comprehensive connectivity model for the human brain is the difficulty in linking Magnetic Resonance Imaging (MRI) measurements to anatomical evidence produced by histological methods. In vivo and postmortem neuroimaging methodologies are still largely incompatible in terms of sample size, scale, and resolution. To help bridge the hiatus between different approaches we have established a program that characterizes the brain of individual subjects, combining MRI with postmortem neuroanatomy. The direct correlation of MRI and histological features is possible, because registered images from different modalities represent the same regions in the same brain. Comparisons are also facilitated by large-scale, digital microscopy techniques that afford images of the whole-brain sections at cellular resolution. The goal is to create a neuroimaging catalog representative of discrete age groups and specific neurological conditions. Individually, the datasets allow for investigating the relationship between different modalities; combined, they provide sufficient predictive power to inform analyses and interpretations made in the context of non-invasive studies of brain connectivity and disease.

Pnn and SR family proteins are differentially expressed in mouse central nervous system

Pinin (pnn) is an SR-related protein that is ubiquitously expressed in most cell types and functions in regulating pre-mRNA splicing and mRNA export. Previously, we demonstrated that pnn is expressed in all tissues during mouse embryonic development with highest levels of expression in the central nervous system (CNS). Here we show that pnn and other SR proteins including SC35 are differentially expressed in the adult mouse CNS, displaying cell type-specific distribution patterns. Immunohistochemical analysis of whole-brain sections showed that levels of pnn and SR proteins expression were very low or nonexistent in the corpus callosum and white matter of cerebellum and spinal cord. Double-immunostaining with antibodies specific to neuron or glial cells showed that most astrocytes and microglia expressed neither pnn nor SR proteins. In contrast, oligodendrocytes and neurons expressed moderate and high levels, respectively, of both pnn and SR proteins. These results suggest that astrocytes are unique among cell types of neuroblast origin in terms of expression SR family proteins. Our results pave the way for future studies of the functional roles of pnn and SR family proteins in adults.

In Vivo Optical Imaging of LacZ Expression Using lacZ Transgenic Mice

beta-Galactosidase (beta-gal) (encoded by the lacZ gene) has been widely used as a transgene reporter enzyme. The ability to image lacZ expression in living transgenic animals would further extend the use of this reporter. It has been reported that 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one)-beta-d-galactopyranoside (DDAOG), a conjugate of beta-galactose and 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one), is not only a chromogenic lacZ substrate but that the cleavage product has far-red fluorescence properties detectable by in vivo imaging. In an attempt to noninvasively image lacZ expression in vivo, we applied fluorescence imaging to a G protein-coupled receptor (GPR56), knockout (KO) mouse model, in which the lacZ gene is introduced in the GPR56 locus. Compared to wild-type (WT) mice, GPR56KO/LacZ mice showed three- to fourfold higher fluorescence intensity in the head area 5 min after tail-vein injection of DDAOG. beta-Gal staining in sections of whole brain showed strong lacZ expression in homozygotes, but not in WT mice, consistent with lacZ activity detected by in vivo imaging. The kidneys were also visualized with fluorescence imaging both in vivo and ex vivo, consistent with beta-gal staining findings. Our results demonstrate that fluorescence imaging can be used for in vivo real-time detection of lacZ activity by fluorescence imaging in lacZ transgenic mice. Thus, this technology can potentially be used to noninvasively image changes of certain endogenous molecules and/or molecular pathways in transgenic animals.

Effect of Gabapentin on c-Fos Expression in the CNS after Paw Surgery in Rats

Gabapentin (neurontin), a GABA analogue anticonvulsant has proven to be effective in anti-nociceptive activity as well as for the treatment of anxiety. Gabapentin (GBP) is well tolerated and shows very favorable side effects profile: The exact molecular mechanism of action of GBP to block postoperative pain and stress is not known. Therefore, to identify the functional neuroanatomical target sites of GBP in post-surgery as well as its effect on postsurgical process, we examined the effects of GBP on c-Fos expression in the supraspinal part of the central nervous system in rats. Using a well-validated rat model of surgical pain, we studied the neuroanatomical functional target sites of gabapentin after paw surgery. The effect of GBP was examined by means of c-Fos immunohistochemistry. A single intraperitoneal injection (i.p.) of GBP (150 mg/kg) or saline (control) was administered 20 min before surgical incision in the paw under anesthesia. Ninety minutes after surgical incision, the deeply anesthetized rats were perfused transcardially with 4% paraformaldehyde. Serial 40-microm-thick sections of whole brain (except spinal cord) were cut and processed by immunohistochemistry to locate and quantify the sites and number of neurons with c-Fos immunoreactivity. Detection of c-Fos protein was performed using the peroxidase-antiperoxidase detection protocol. Our present study demonstrated that compared to control, administration of GBP (150 mg/kg, i.p.) before paw surgery significantly (p < 0.01) attenuated the incision-induced c-Fos expression only in the paraventricular nucleus of the hypothalamus. In addition, GBP-induced increase in c-Fos expression was observed in the dorsal raphe (DRN) and in the nucleus raphe magnus. Present results indicate that GBP may differentially modulate c-Fos expression in surgical paw incision. Moreover, this study provides some clue to examine whether GBP exerts its action simultaneously through two separate pathways in post-surgery.

Alpha‐1A Adrenergic Receptor Overexpression Protects Hippocampal Interneurons

A variety of cytochemically distinct cellular profiles have been shown within the hippocampus, however the synaptic elements whereby the abundant adrenergic input mediates its action remain obscure. Additionally, the lack of highly specific adrenergic receptor (AR) antibodies has reduced the confidence of specific localization of the receptor proteins. To address this issue, a novel model system was utilized in which transgenic mice over-express the α1A or α1B-AR fused with EGFP. Sagittal sections of whole brain were double labeled with markers of specific subpopulations of hippocampal neurons and ARs labeled with an anti-EGFP antibody. Mice which overexpress α1B-ARs were found to have an age-dependent decrease in the number of hippocampal interneurons. In contrast, mice overexpressing α1A-ARs had significantly more hippocampal interneurons. Interestingly, mice overexpressing α1B-ARs show an increase in seizure development. Alternatively, α1A-AR overexpression appears to control seizure development through regulation of interneuron function. These results provide anatomical evidence that α1A or α1B-AR subunits have a diverse distribution among hippocampal neurons with distinct functional identities, which may serve as potential therapeutic targets. This study was funded in part by NIH RO1HL61438 (DMP), NSF CAREER Award 0347259 (VAD), and NIH 5P20RR017699 from the COBRE program (PAC, VAD).

White matter mapping in Alzheimer's disease: A neuropathological study

White matter disease (WMD) with pervasive non-focal subtotal tissue loss is frequently seen in Alzheimer's disease (AD) upon neuropathological examination. Although WMD has varying effects on AD symptoms, accurate clinical detection is difficult due partly to scarcity of correlative structural imaging and histopathological studies. Neuropathological studies of WMD severity and distribution have been conducted earlier using semi-quantitative methods. A technique for quantifying WMD objectively in large white matter areas, based on optical density (OD) measurements on images of scanned whole-brain sections, was developed and was validated using conventional microscopic assessment. Altogether, 16 AD cases with concomitant WMD (AD–WMD) and 9 cases of AD without WMD (AD-only) were analysed. The OD values correlated significantly with the neuropathological severity of WMD and were significantly lower in AD–WMD than in AD-only in frontal, frontoparietal, temporal and parietal white matter but not in the occipital white matter, the frontal OD difference being greatest. Useful baseline information on WMD distribution in AD to relate to in vivo imaging results was obtained.