Design-based stereology in neuroscience

Efficient estimation of retinal ganglion cell number: a stereological approach

Retinal ganglion cells (RGCs) are the only output neurons of the retina, and their degeneration after damage to the optic nerve or in glaucoma is a well established system for studying apoptosis in the central nervous system. Frequently used procedures for assessing RGC number in retinal flat mounts suffer from two problems: RGC densities are not uniform across retinal flat mounts, and density measures may therefore not reflect total number, and flat mounts do not allow efficient use of tissue. To overcome these problems we developed a stereological method for efficiently assessing RGC number in cryostat sections of the retina. We empirically demonstrate that only approximately 1:20 sections need be assessed to accurately estimate the total number of RGCs in the rat retina, providing ample tissue for additional studies in the same retina and saving considerably on more exhaustive sampling strategies. Using this method, we estimate that there are 86,282+/-4759 RGCs in the normal Brown Norway rat retina. These counts match well with estimates of axon counts in optic nerve. In a pilot study of experimental glaucoma, we determined a reduction of RGCs to 53,862+/-4272 (p<0.05). The current technique should prove advantageous to assess neuroprotective strategies in these experimental models.

Neuroprotective effect of aminoguanidine on iron-induced neurotoxicity

Iron is a commonly used metal to induce neuronal hyperactivity and oxidative stress. Iron levels rise in the brain in some neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. A body of evidence indicates a link between neuronal death and nitric oxide. The present study was performed to investigate whether nitric oxide produced by inducible nitric oxide synthase is involved in iron-induced neuron death. For this purpose rats were divided into four groups: control, iron, aminoguanidine and iron+aminoguanidine. Animals in iron and iron+aminoguanidine groups received intracerebroventricular FeCl3 injection (200 mM, 2.5 microl). Rats belonging to control and aminoguanidine groups received the same amount of saline into the cerebral ventricles. All animals were kept alive for 10 days following the operation and animals in aminoguanidine and iron+aminoguanidine groups received intraperitoneal aminoguanidine injections once a day (100mg/kg day) during this period. After 10 days, rats were perfused intracardially under deep urethane anesthesia. Removed brains were processed using the standard histological techniques. The total numbers of neurons in hippocampus of all rats were estimated with the unbiased stereological techniques. It was found that aminoguanidine decreased mean neuron loss from 43.4% to 20.3%. Results of the present study suggest that aminoguanidine may attenuate the neurotoxic effects of iron by inhibiting inducible nitric oxide synthase.

Brief treatment with the glucocorticoid receptor antagonist mifepristone normalizes the reduction in neurogenesis after chronic stress

In rodents, stress suppresses adult neurogenesis. This is thought to involve activation of glucocorticoid receptors in the brain. In the present study, we therefore questioned whether glucocorticoid receptor blockade by mifepristone can normalize the effects of chronic stress on adult neurogenesis. Rats received mifepristone on the last 4 days of a 21-day chronic unpredictable and inescapable stress regimen. Neurogenesis was analysed by stereological quantification of adult-generated cell survival (bromodeoxyuridine), young neuronal survival (doublecortin) and cell proliferation (Ki-67). The results show that only 4 days of mifepristone treatment normalized the stress-induced reductions in neurogenesis. Importantly, mifepristone by itself had no effect on neurogenesis. We conclude that, contrary to other compounds interfering with the effects of chronic stress on neurogenesis, like antidepressants, the normalizing effects of mifepristone on neurogenesis are rapid and particularly potent in a high stress environment. This neurogenic action of mifepristone could potentially contribute to its clinical mechanism of action.

Spatial arrangement of microglia in the mouse hippocampus: a stereological study in comparison with astrocytes

Microglia are classically considered to be immune cells in the brain, but have now been proven to be involved in neuronal activity as well. Here we stereologically analyzed the spatial arrangement of microglia in the mouse hippocampus. First, we estimated the numerical densities (NDs) of microglia identified by ionized calcium-binding adaptor molecule 1 (Iba1). Despite that microglia appeared to be evenly distributed throughout the hippocampal area, the NDs demonstrated significant dorsoventral, interregional, and interlaminar differences. Briefly, the NDs in the ventral hippocampus were significantly lower in the CA3 region than in the CA1 region and dentate gyrus, although no interregional differences were detectable in the dorsal hippocampus. Both in the CA1 and CA3 regions, the NDs were significantly higher in the stratum lacunosum-moleculare than in the remaining layers. Next, we investigated the spatial patterns of distribution of Iba1-labeled microglia and S100beta-labeled astrocytes. So far as we examined, the somato-somatic contacts were not seen among microglia or among astrocytes, whereas the close apposition between microglia and astrocytes were occasionally detected. The 3D point process analysis showed that the spatial distribution of microglia was significantly repulsive. Because the statistical territory of single microglia was larger than that estimated from process tracing, they are not likely to touch each other with their processes. Astrocytes were distributed slightly repulsively with overlapping areas. The 3D point process analysis also revealed a significant spatial attraction between microglia and astrocytes. The present findings provide a novel anatomical basis for glial research.

Autism post-mortem neuroinformatic resource: the autism tissue program (ATP) informatics portal

The Autism Tissue Program (ATP) was established to oversee and manage brain donations related to neurological research in autism. The ATP Informatics Portal (www.atpportal.org) is an integrated data access system based on Oracle technology, developed to provide access for researchers to information on this rare tissue resource. It also permits sorting of existing cases based on donor ante-mortem history as well as agonal states and post-mortem tissue conditions. Phase II of development established administrative tracking of registrants intending to donate, as well as management of tissue requests and the awarding and tracking of tissue. Phase III is the ongoing assimilation of data sets derived from research on a core group of donors with searchable access by investigators.

Elevated dopamine levels during gestation produce region-specific decreases in neurogenesis and subtle deficits in neuronal numbers

Dopamine levels in the fetal brain were increased by administering the dopamine precursor 3,4-dihydroxy-l-phenylalanine (l-DOPA) to pregnant mice in drinking water. The l-DOPA exposure decreased bromodeoxyuridine (BrdU) labeling in the lateral ganglionic eminence and frontal cortical neuroepithelium but not medial or caudal ganglionic eminences. The regional differences appear to reflect heterogeneity in precursor cells' responses to dopamine receptor activation. Relative numbers of E15-generated neurons were decreased at postnatal day 21 (P21) in the caudate-putamen, nucleus accumbens and frontal cortex but not globus pallidus in the l-DOPA group. TUNEL labeling did not show significant differences on P0, P7 or P14 in the caudate-putamen or frontal cortex, suggesting that cell death was not altered. Although virtually all cells in the P21 brains that were labeled with the E15 BrdU injection were NeuN-positive, stereological analyses showed no significant changes in total numbers of NeuN-positive or NeuN-negative cells in the P21 caudate-putamen or frontal cortex. Thus persisting deficits in neuronal numbers were evident in the l-DOPA group only by birth-dating analyses and not upon gross histological examination of brain sections or analysis of total numbers of neurons or glia. One explanation for this apparent discrepancy is that l-DOPA exposure decreased cell proliferation at E15 but not at E13. By E15, expansion of the neuroepithelial precursor pool is complete and any decrease in cell proliferation likely produces only marginal decreases in the total numbers of cells generated. Our l-DOPA exposure model may be pertinent to investigations of neurological dysfunction produced by developmental dopamine imbalance.

Comparative analysis of adeno-associated viral vector serotypes 1, 2, 5, 7, and 8 in mouse brain

Recombinant adeno-associated virus serotype 2 (rAAV2) vectors have been shown to deliver genes effectively to neurons in the brain, retina, and spinal cord. The characterization of new AAV serotypes revealed different patterns of transduction in a diverse array of tissues (Gao, G., Vandenberghe, L.H., and Wilson, J.M. [2005]. Curr. Gene Ther. 5, 285-297). Here, we extensively compare the neural tropism of human-derived rAAVs (types 2/1, 2, and 2/5) with nonhuman primate-derived rAAVs (types 2/7 and 2/8) in adult mouse brain. Mice were injected with rAAV type 2/1, 2, 2/5, 2/7, or 2/8 via the caudate-putamen and substantia nigra. Intrahippocampal injections were also performed for rAAV2/7 and rAAV2/8. In all regions injected, the vectors transduced neurons almost exclusively. Retrograde transduction of all rAAV pseudotypes was also observed in particular CNS areas. At high titers, all rAAV pseudotypes transduced comparable brain volumes in all targeted regions except for rAAV2, which transduced much smaller brain volumes. A dose-range comparison of intrastriatally injected rAAV types 2/5, 2/7, and 2/8 highlighted that the transduction efficiency, as determined by transduced volume and biophotonic imaging of green fluorescent protein expression intensity, was significantly higher for rAAV2/5 and rAAV2/7 compared with rAAV2/8 at low titers, whereas all three serotypes performed equally well at higher doses. These results demonstrate the use and efficiency of both human- and nonhuman primate-derived rAAV vectors for disease modeling and their potential for gene therapy.

High frequency stimulation of the subthalamic nucleus improves speed of locomotion but impairs forelimb movement in Parkinsonian rats

The subthalamic nucleus (STN) plays an important role in motor and non-motor behavior in Parkinson's disease, but its involvement in gait functions is largely unknown. In this study, we investigated the role of the STN on gait in a rat model of PD using the CatWalk method. Parkinsonian rats received bilateral high frequency stimulation (HFS) with different stimulation amplitudes of the STN. Rats were rendered parkinsonian by bilateral injections of 6-hydroxydopamine (6-OHDA) into the striatum. One group of 6-OHDA animals was implanted bilaterally with stimulation electrodes at the level of the STN. Stimulations were performed at 130 Hz (frequency), 60 micros (pulse width) and varying amplitudes of 0, 3, 30 and 150 microA. Rats were evaluated in an automated quantitative gait analysis method (CatWalk method). After behavioral evaluations, rats were killed and the brains processed for histological stainings to determine the impact of the dopaminergic lesion (tyrosine hydroxylase immunohistochemistry) and the localization of the electrode tip (hematoxylin-eosin histochemistry). Results show that bilateral 6-OHDA infusion significantly decreased (70%) the number of dopaminergic cells in the substantia nigra pars compacta (SNc). Due to 6-OHDA treatment, the gait parameters changed considerably. There was a general slowness. The most pronounced effects were seen at the level of the hind paws. Due to implantation of STN electrodes the step pattern changed. STN electrical stimulation improved the general slowness but induced slowing of the forelimb movement. Furthermore, we found that HFS with a medium amplitude significantly changed speed, the so-called dynamic aspect of gait. The static features of gait were only significantly influenced with low amplitude. Remarkably, STN stimulation affected predominantly the forepaws/limbs.

Innate and adaptive immunity during epileptogenesis and spontaneous seizures: evidence from experimental models and human temporal lobe epilepsy

We investigated the activation of the IL-1 beta system and markers of adaptive immunity in rat brain during epileptogenesis using models of temporal lobe epilepsy (TLE). The same inflammatory markers were studied in rat chronic epileptic tissue and in human TLE with hippocampal sclerosis (HS). IL-1 beta was expressed by both activated microglia and astrocytes within 4 h from the onset of status epilepticus (SE) in forebrain areas recruited in epileptic activity; however, only astrocytes sustained inflammation during epileptogenesis. Activation of the IL-1 beta system during epileptogenesis was associated with neurodegeneration and blood-brain barrier breakdown. In rat and human chronic epileptic tissue, IL-1 beta and IL-1 receptor type 1 were broadly expressed by astrocytes, microglia and neurons. Granulocytes appeared transiently in rat brain during epileptogenesis while monocytes/macrophages were present in the hippocampus from 18 h after SE onset until chronic seizures develop, and they were found also in human TLE hippocampi. In rat and human epileptic tissue, only scarce B- and T-lymphocytes and NK cells were found mainly associated with microvessels. These data show that specific inflammatory pathways are chronically activated during epileptogenesis and they persist in chronic epileptic tissue, suggesting they may contribute to the etiopathogenesis of TLE.

Sulcal variability, stereological measurement and asymmetry of Broca's area on MR images

Leftward volume asymmetry of the pars opercularis and pars triangularis may exist in the human brain, frequently referred to as Broca's area, given the functional asymmetries observed in this region with regard to language expression. However, post-mortem and magnetic resonance imaging (MRI) studies have failed to consistently identify such a volumetric asymmetry. In the present study, an analysis of the asymmetry of sulco-gyral anatomy and volume of this anterior speech region was performed in combination with an analysis of the morphology and volume asymmetry of the planum temporale, located within the posterior speech region, in 50 healthy subjects using MRI. Variations in sulcal anatomy were documented according to strict classification schemes and volume estimation of the grey matter within the brain structures was performed using the Cavalieri method of stereology. Results indicated great variation in the morphology of and connectivity between the inferior frontal, inferior precentral and diagonal sulci. There were significant inter-hemispheric differences in the presence of (1) the diagonal sulcus within the pars opercularis, and (2) horizontal termination of the posterior Sylvian fissure (relative to upward oblique termination), both with an increased leftward incidence. Double parallel inferior precentral sulci and absent anterior rami of the Sylvian fissure prevented stereological measurements in five subjects. Therefore volumes were obtained from 45 subjects. There was a significant leftward volume asymmetry of the pars opercularis (P = 0.02), which was significantly related to the asymmetrical presence of the diagonal sulcus (P < 0.01). Group-wise pars opercularis volume asymmetry did not exist when a diagonal sulcus was present in both or neither hemispheres. There was no significant volume asymmetry of the pars triangularis. There was a significant leftward volume asymmetry of the planum temporale (P < 0.001), which was significantly associated with the shape of the posterior Sylvian fissure as a unilateral right or left upward oblique termination was always associated with leftward or rightward volume asymmetry respectively (P < 0.01). There was no relationship between volume asymmetries of the anterior and posterior speech regions. Our findings illustrate the extent of morphological variability of the anterior speech region and demonstrate the difficulties encountered when determining volumetric asymmetries of the inferior frontal gyrus, particularly when sulci are discontinuous, absent or bifid. When the intrasulcal grey matter of this region is exhaustively sampled according to strict anatomical landmarks, the volume of the pars opercularis is leftward asymmetrical. This manuscript illustrates the importance of simultaneous consideration of brain morphology and morphometry in studies of cerebral asymmetry.

Lesions of dopaminergic neurons in the substantia nigra pars compacta and in the ventral tegmental area enhance depressive-like behavior in rats

Depression is the most common psychiatric complication in Parkinson's disease (PD). The pathophysiological events leading to PD-associated depression, however, remain largely unknown. The present study tested the differential implication of dopaminergic systems in depressive-like behavior in rats and its response to l-Dopa and the selective serotonin reuptake inhibitor citalopram. The learned helplessness model was used as a behavioral paradigm. Rats were lesioned in the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) and assigned to subgroups with respect to the stereologically verified extent of the nigral and/or VTA degeneration. Both lesions increased depressive-like behavior in rats, which was reduced by both citalopram and l-Dopa treatment. We conclude that dopaminergic lesions of either the SNc or the VTA contribute to the manifestation of depressive-like behavior in rats. The effects of citalopram administration on depressive behavior induced by lesions of dopaminergic brain regions furthermore suggest an involvement of serotonergic pathways in dopaminergic cell loss-induced depression.

Unique responses to mitochondrial complex I inhibition in tuberoinfundibular dopamine neurons may impart resistance to toxic insult

Tuberoinfundibular dopamine (TIDA) neurons are spared in Parkinson's disease (PD), a disorder that causes degeneration of midbrain nigrostriatal dopamine (NSDA) and mesolimbic dopamine (MLDA) neurons. This pattern of susceptibility has been demonstrated in acute complex I inhibitor-induced models of PD, and extrinsic factors such as toxin distribution, bioactivation, entry into the cell and sequestration into vesicles are postulated to underlie the resistance of TIDA neurons. In the present experiments, direct exposure to rotenone or 1-methyl-4-phenylpyridinium (MPP+) had no effect on mediobasal hypothalamic TIDA neurons, but significantly increased the percentage of apoptag immunoreactive neurons in midbrain primary NSDA and MLDA cultures. In vivo 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposure caused an initial decrease (by 4 h) in dopamine (DA) in brain regions containing axon terminals of TIDA (median eminence [ME]), NSDA (striatum [ST]) and MLDA (nucleus accumbens [NA]) neurons. By 16 h after MPTP treatment, DA concentrations in ME returned to control levels, while ST and NA DA levels remained low up to 32 h after treatment with MPTP. When mice and rats were chronically treated with MPTP and rotenone, respectively, the same pattern of susceptibility emerged. TIDA neurons were unaffected while NSDA neurons suffered loss of cell bodies and axon terminal DA. These experiments demonstrate that the resistance of hypothalamic TIDA neurons is not likely to be due to extrinsic factors, and that further examination of the intrinsic properties of these neurons may elucidate mechanisms that can be translated into neuroprotective strategies in PD.

The length of hippocampal cholinergic fibers is reduced in the aging brain

Cholinergic deficits occur in the aged hippocampus and they are significant in Alzheimer's disease. Using stereological and biochemical approaches, we characterized the cholinergic septohippocampal pathway in old (24 months) and young adult (3 months) rats. The total length of choline acetyltransferase (ChAT)-positive fibers in the dorsal hippocampus was significantly decreased by 32% with aging (F((1,9))=20.94, p=0.0014), along with the levels of synaptophysin, a presynaptic marker. No significant changes were detected in ChAT activity or in the amounts of ChAT protein, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), tropomyosin related kinase receptor (Trk) A, TrkB, or p75 neurotrophin receptor (p75(NTR)) in the aged dorsal hippocampus. The number and size of ChAT-positive neurons and the levels of ChAT activity, NGF and BDNF were not statistically different in the septum of aged and young adult rats. This study suggests that substantial synaptic loss and cholinergic axonal degeneration occurs during aging and reinforces the importance of therapies that can protect axons and promote their growth in order to restore cholinergic neurotransmission.

Moderate loss of cerebellar Purkinje cells after chronic bilateral common carotid artery occlusion in rats

Pathological effects of moderate ischemia (oligemia, hypoperfusion) are relevant in relation to vascular factors in dementia. Chronic bilateral common carotid artery occlusion (BCCAO) in adult Wistar rats induces oligemia and leads to acute changes in gene expression, subacute changes in cortical astrocytes and prolonged changes in white matter tracts, while largely sparing neurons in the forebrain areas. Dilation and remodeling of the basilar artery ensures blood flow to the forebrain. The present study examined the hypoxia-sensitive Purkinje cells in the cerebellum after 6 months of BCCAO using conventional neuropathological analysis, immunohistochemistry and high-precision design-based stereologic methods. Purkinje cells in the vermis region revealed abnormally shaped nuclei. A stereologic analysis showed that the mean total number of Purkinje cells within the vermis was statistically significantly smaller in the BCCAO animals than in the control animals (d = 11.8%; P < 0.0001). BCCAO had no significant effect on the mean volumes of the molecular layer, granule cell layer and white matter in the vermis or the entire cerebellum. Remodeling of the basilar artery indicated that secondary vascular perturbations might be responsible for the effects of BCCAO on the cerebellar Purkinje cells.

Stereological analysis of neuropil threads in the hippocampal formation: relationships with Alzheimer's disease neuronal pathology and cognition

Although neuropil threads are thought to account for 85-90% of cortical tau pathology in brain ageing, their clinical significance remains controversial. Previous studies have measured densities, rather than absolute numbers, and most did not take into account possible interactions among the pathological hallmarks of Alzheimer's disease (AD). We report here stereological estimates of total neurofibrillary tangle (NFT) and neuron numbers as well as total amyloid volume and neuropil thread (NT) length, in the hippocampus and entorhinal cortex of 19 very old individuals (age range: 83-101 years) with various degrees of cognitive decline. Total NT length in all areas studied increased in mildly demented cases but showed a marked decrease in Clinical Dementia Rating (CDR) scale 3 cases. Both total NFT and neuron numbers were related to NT length in the CA1 field and entorhinal cortex. A strong positive relationship was also present between the total NFT numbers in the entorhinal cortex and NT length in the CA1 field and dentate gyrus. Total NT length in the CA1 field was related to both CDR scores and presence or absence of dementia explaining 7% and 37% of their variability respectively. In multivariate models, this relationship was highly dependent on the severity of NFT formation in this area. Our data reveal that NT formation in hippocampal subdivisions and entorhinal cortex accompanies AD neuronal pathology in early stages of the degenerative process, yet its rate may decrease in severe dementia. In terms of clinicopathological correlations, NT length in the hippocampal formation does not represent an independent marker of dementia severity.

Stereologic estimates of total spinophilin-immunoreactive spine number in area 9 and the CA1 field: relationship with the progression of Alzheimer's disease

The loss of presynaptic markers is thought to represent a strong pathologic correlate of cognitive decline in Alzheimer's disease (AD). Spinophilin is a postsynaptic marker mainly located to the heads of dendritic spines. We assessed total numbers of spinophilin-immunoreactive puncta in the CA1 and CA3 fields of hippocampus and area 9 in 18 elderly individuals with various degrees of cognitive decline. The decrease in spinophilin-immunoreactivity was significantly related to both Braak neurofibrillary tangle (NFT) staging and clinical severity but not A beta deposition staging. The total number of spinophilin-immunoreactive puncta in CA1 field and area 9 were significantly related to MMSE scores and predicted 23.5 and 61.9% of its variability. The relationship between total number of spinophilin-immunoreactive puncta in CA1 field and MMSE scores did not persist when adjusting for Braak NFT staging. In contrast, the total number of spinophilin-immunoreactive puncta in area 9 was still significantly related to the cognitive outcome explaining an extra 9.6% of MMSE and 25.6% of the Clinical Dementia Rating scores variability. Our data suggest that neocortical dendritic spine loss is an independent parameter to consider in AD clinicopathologic correlations.

Complete or partial hippocampal damage produces equivalent retrograde amnesia for remote contextual fear memories

We examined the effects of partial or complete damage to the hippocampus on long-term retention of a Pavlovian conditioned fear response to context. Rats received a single contextual fear-conditioning episode and 1 week, 3 months or 6 months later they received sham, partial (dorsal) or complete NMDA-induced damage of the hippocampus. During a retention test conducted 2 weeks after surgery, the control rats exhibited high levels of freezing in the context, although their level of freezing was significantly lower with longer retention intervals. Rats with complete hippocampal damage displayed very little freezing in the context at each learning-surgery interval. Partial hippocampal damage caused a smaller but consistent deficit in conditioned responding, especially at longer learning-surgery intervals. Neither group of hippocampus-damaged rats showed less retrograde amnesia for more remote memories. We found that the severity of retrograde amnesia for contextual fear conditioning following hippocampal damage is related to the extent of the damage and that there is consistent and severe retrograde amnesia for even remote contextual fear memories. These findings support the idea that the hippocampal formation has an essential and long-lasting, possibly permanent, role in memory for contexts.

Consolidation of object-discrimination memory is independent of the hippocampus in rats

We examined whether retrograde amnesia would be more likely for object discriminations learned an hour before hippocampal damage than object discriminations learned days before. Specifically, rats were trained on two object-discrimination problems 72 h before surgery and another discrimination problem and the reversal of one of the previously learned problems 1 h before surgery. Importantly, novel procedures that minimized overtraining on the object discriminations were used to increase the possibility of the lesions causing amnesia. After either receiving sham or neurotoxic-induced hippocampal damage, rats were tested for retention using an extinction procedure. Control rats and rats with extensive hippocampal damage displayed a strong bias for the rewarded object on each object-discrimination problem and a significant bias for the most recent contingency learned on the reversal problem. These results suggest that, despite the use of very sensitive training and testing procedures, hippocampal damage did not cause retrograde amnesia. The findings imply that the hippocampus is not critical for the consolidation, storage, or retrieval of object-reward associations, or any other information required for accurate performance of an object discrimination.

Differential neurogenesis in the adult rat dentate gyrus: an identifiable zone that consistently lacks neurogenesis

The dentate gyrus continues to produce new neurons in adult rodents. The possibility of differential regulation of neurogenesis within regions of the dentate gyrus is largely unexplored, despite several other aspects of this phenomenon being well characterized in a large number of studies. In this report, we describe an area located at the anterior pole of the dentate gyrus that consistently lacks neurogenesis. This neurogenically quiescent zone invariably lacks expression of the neuroblast marker doublecortin (DCX), bromodeoxyuridine and Ki-67, though DCX expression can be elicited in response to a combined paradigm of environmental enrichment and wheel running. We propose that this region may provide a valuable model system to discern the factors that regulate the process of neurogenesis.

Volume, neuron density and total neuron number in five subcortical regions in schizophrenia

Several studies have pointed to alterations in mean volumes, neuron densities and total neuron numbers in the caudate nucleus (CN), putamen, nucleus accumbens (NA), mediodorsal nucleus of the thalamus (MDNT) and lateral nucleus of the amygdala (LNA) in schizophrenia. However, the results of these studies are conflicting and no clear pattern of alterations has yet been established in these subcortical regions, possibly due to differences in quantitative histological methods used as well as differences in the investigated case series. The present study investigates these subcortical regions in both hemispheres of the same post-mortem brains for volume, neuron density and total neuron number with high-precision design-based stereology. The analysed case series consisted of 13 post-mortem brains from male schizophrenic patients [age range: 22-64 years; mean age 51.5 +/- 3.3 years (mean +/- SEM)] and 13 age-matched male controls (age range: 25-65 years; mean age 51.9 +/- 3.1 years). A general linear model multivariate analysis of variance with diagnosis and hemisphere as fixed factors and illness duration (schizophrenic patients) or age (controls), post-mortem interval and fixation time as covariates showed a number of statistically significant alterations in the brains from schizophrenic patients compared with the controls. There was a reduced mean volume of the putamen [-5.0% on the left side (l) and -4.1% on the right side (r)] and the LNA (l: -12.1%, r: -17.6%), and a reduced mean total neuron number in the CN (l: -10.4%, r: -10.2%), putamen (l: -8.1%, r: -11.6%) and the LNA (l: -15.9%, r: -16.2%). These data show a previously unreported, distinct pattern of alterations in mean total neuron numbers in identified subcortical brain regions in a carefully selected sample of brains from schizophrenic patients. The rigorous quantitative analysis of several regions in brains from schizophrenic patients and matched controls is crucial to provide reliable information on the neuropathology of schizophrenia as well as insights about its pathogenesis.

Long-term cognitive impairment, neuronal loss and reduced cortical cholinergic innervation after recovery from sepsis in a rodent model

Sepsis is a disease with a high and growing prevalence worldwide. Most studies on sepsis up to date have been focused on reduction of short-term mortality. This study investigates cognitive and neuroanatomical long-term consequences of sepsis in a rat model. Sepsis was induced in male Wistar rats weighing 250-300 g by an i.p. injection of bacterial lipopolysaccharide (LPS, 10 mg/kg). Three months after complete recovery from sepsis, animals showed memory deficits in the radial maze and changes in open field exploratory patterns but unaffected inhibitory avoidance learning. Behavioral findings were matched by sepsis-induced loss of neurons in the hippocampus and the prefrontal cortex on serial sections after NeuN-staining and reduced cholinergic innervation in the parietal cortex measured by immunoradiography of vesicular acetylcholine transporter (VAChT). Together these results suggest that sepsis can induce persistent behavioral and neuroanatomical changes and warrant studies of the neurological long-term consequences of sepsis in humans.

The aging brain: Accumulation of DNA damage or neuron loss?

Age-related molecular and cellular alterations in the central nervous system are known to show selectivity for certain cell types and brain regions. Among them age-related accumulation of nuclear (n) DNA damage can lead to irreversible loss of genetic information content. In the present study on the aging mouse brain, we observed a substantial increase in the amount of nDNA single-strand breaks in hippocampal pyramidal and granule cells as well as in cerebellar granule cells but not in cerebellar Purkinje cells. The reverse pattern was found for age-related reductions in total numbers of neurons. Only the total number of cerebellar Purkinje cells was significantly reduced during aging whereas the total numbers of hippocampal pyramidal and granule cells as well as of cerebellar granule cells were not. This formerly unknown inverse relation between age-related accumulation of nDNA damage and age-related loss of neurons may reflect a fundamental process of aging in the central nervous system.

Network modeling of adult neurogenesis: shifting rates of neuronal turnover optimally gears network learning according to novelty gradient

Apoptotic and neurogenic events in the adult hippocampus are hypothesized to play a role in cognitive responses to new contexts. Corticosteroid-mediated stress responses and other neural processes invoked by substantially novel contextual changes may regulate these processes. Using elementary three-layer neural networks that learn by incremental synaptic plasticity, we explored whether the cognitive effects of differential regimens of neuronal turnover depend on the environmental context in terms of the degree of novelty in the new information to be learned. In "adult" networks that had achieved mature synaptic connectivity upon prior learning of the Roman alphabet, imposition of apoptosis/neurogenesis before learning increasingly novel information (alternate Roman < Russian < Hebrew) reveals optimality of informatic cost benefits when rates of turnover are geared in proportion to the degree of novelty. These findings predict that flexible control of rates of apoptosis-neurogenesis within plastic, mature neural systems optimizes learning attributes under varying degrees of contextual change, and that failures in this regulation may define a role for adult hippocampal neurogenesis in novelty- and stress-responsive psychiatric disorders.

Retrograde labeling reveals extensive distribution of genioglossal motoneurons possessing 5-HT2A receptors throughout the hypoglossal nucleus of adult dogs

Inspiratory hypoglossal motoneurons (IHMNs) innervate the muscles of the tongue and play an important role in maintaining upper airway patency. However, this may be reduced during sleep and by sedatives, potent analgesics, and volatile anesthetics. The genioglossal (GG) muscle is the main protruder and depressor muscle of the tongue and contributes to upper airway patency during inspiration. In vitro data suggest that serotonin (5-hydroxytryptamine, 5-HT), via the 5-HT(2A) receptor (5-HT(2A)R) subtype, plays a key role in controlling the excitability of IHMNs. The distribution of GG motoneurons (GGMNs) within the hypoglossal (XII) nucleus has not been studied in the adult dog. Further, it is uncertain whether the 5-HT(2A)R is located on GGMNs in the adult dog. We therefore used the cholera toxin B (CTB) subunit as a retrograde tracer to map the location of GGMNs in combination with immunofluorescent labeling to determine the presence and colocalization of 5-HT(2A)R within the XII nucleus in adult mongrel dogs. Injection of CTB into the GG muscle resulted in retrogradely labeled cells in a compact column throughout the XII nucleus, extending from 0.75 mm caudal to 3.45 mm rostral to the obex. Fluorescence immunohistochemistry revealed extensive 5-HT(2A)R labeling on CTB-labeled GGMNs. Identification of the 5-HT(2A)R on GGMNs in the XII nucleus of the adult dog supports in vitro data and suggests a physiological role for this receptor subtype in controlling the excitability of GGMNs, which contribute to the maintenance of upper airway patency.

How a neuropsychiatric brain bank should be run: a consensus paper of Brainnet Europe II

The development of new molecular and neurobiological methods, computer-assisted quantification techniques and neurobiological investigation methods which can be applied to the human brain, all have evoked an increased demand for post-mortem tissue in research. Psychiatric disorders are considered to be of neurobiological origin. Thus far, however, the etiology and pathophysiology of schizophrenia, depression and dementias are not well understood at the cellular and molecular level. The following will outline the consensus of the working group for neuropsychiatric brain banking organized in the Brainnet Europe II, on ethical guidelines for brain banking, clinical diagnostic criteria, the minimal clinical data set of retrospectively analyzed cases as well as neuropathological standard investigations to perform stageing for neurodegenerative disorders in brain tissue. We will list regions of interest for assessments in psychiatric disorder, propose a dissection scheme and describe preservation and storage conditions of tissue. These guidelines may be of value for future implementations of additional neuropsychiatric brain banks world-wide.

Efficient quantitative morphological phenotyping of genetically altered organisms using stereology

Genetically modified organisms present the challenge of quantifying structures and functions in organs, tissues and cells. Morphological investigation is greatly facilitated by taking sections in MRI, CAT scanning, histological preparations or EM, and powerful unbiased quantitative tools called stereology can use these sections in a sampling based approach to measure volume, number surface and length. Stereological tools have become methods of choice in the fields of neurobiology, nephrology and cell biology and allow accurate unbiased description of intact organs, tissues, cells and organelles. Stereology has yet to be applied widely in the field of transgenics. Here I provide an overview of stereological methods and explain how they represent a powerful addition to the transgenic biologists armoury of techniques.

Protection of nigral cell death by bilateral subthalamic nucleus stimulation

In Parkinson disease (PD), the subthalamic nucleus (STN) becomes hyperactive (disinhibited), which is reported to cause excitotoxic damage to midbrain dopaminergic neurons. Here, we examined whether silencing of the hyperactive STN by chronic bilateral deep brain stimulation (DBS) increased the survival of midbrain dopaminergic neurons in a rat model of PD. High-precision design-based stereologic examination of the total number of neurons and tyrosine tydroxylase (TH) immunoreactive neurons in the substantia nigra pars compacta revealed that STN DBS resulted in a significant survival of these neurons. These data provide the first evidence in vivo that bilateral STN DBS is useful for protecting midbrain dopaminergic neurons from cell death in PD.

Parkin Protects against Neurotoxicity in the 6-Hydroxydopamine Rat Model for Parkinson's Disease

Loss-of-function mutations in the PARK2 gene are the major cause of early onset familial Parkinson's disease. The gene product, parkin, is an E3 ligase of the ubiquitin-proteasome pathway involved in protein degradation. Dopaminergic neuron loss may result from the toxic accumulation of parkin substrates, suggesting a key role for parkin in dopaminergic neuron survival. In this study, we have investigated the neuroprotective capacity of parkin in the 6-OHDA rat model for Parkinson's disease. 6-OHDA induces the generation of reactive oxygen species leading to the degeneration of catecholaminergic neurons, but may also impair proteasome activity. Lentiviral vectors encoding human wild-type parkin or green fluorescent protein were stereotactically injected into the substantia nigra 2 weeks prior to a striatal 6-OHDA lesion. Histological analysis 1 and 3 weeks after lesioning showed a significant preservation of dopaminergic cell bodies and nerve terminals. Moreover, lesioned rats overexpressing parkin displayed a corresponding behavioral improvement as measured by the amphetamine-induced rotation test and the cylinder test. The improved performance in the amphetamine-induced rotation test lasted until 20 weeks after lesioning. Our results demonstrate that parkin acts as a potent neuroprotective agent in vivo against 6-OHDA toxic insults. These data support the therapeutic potential of parkin for the treatment of not only familial but also sporadic Parkinson's disease.

GABAergic structures in the ventral part of the oral pontine reticular nucleus: An ultrastructural immunogold analysis

GABA mediates inhibitory effects in neurons of the ventral part of the oral pontine reticular nucleus (vRPO). Evidence increasingly suggests that GABA plays an important role in the modulation of rapid eye movement (REM) sleep generation in the cat vRPO. Here, we investigate the anatomical substrate of this modulation using GABA immunocytochemistry. Immunoperoxidase labeling revealed a few small GABA-immunoreactive cell bodies scattered throughout the vRPO. The numerical densities of all vRPO synapses and the GABA-immunoreactive synapses were estimated, at the electron microscopical level, by using a combination of the physical disector and the post-embedding immunogold techniques. We estimated that 30% of all vRPO synaptic terminals were immunoreactive to GABA. Our findings support the hypothesis that vRPO neuron activity is significantly controlled by inhibitory GABAergic terminals that directly target somata and the different parts of the dendritic tree, including distal regions. GABAergic input could inhibit vRPO REM sleep-inducing neurons during other states of the sleep-wakefulness cycle such as wakefulness or non-REM sleep.

Differential disruption of nuclear volume and neuronal phenotype in the preoptic area by neonatal exposure to genistein and bisphenol-A

Changes in the volumes of sexually dimorphic brain nuclei are often used as a biomarker for developmental disruption by endocrine-active compounds (EACs). However, these gross, morphological analyses do not reliably predict disruption of cell phenotype or neuronal function. In the present experiments, we used a more comprehensive approach to assess whether postnatal exposure to the EACs genistein (GEN) or bisphenol-A (BIS) affected the development of two sexually dimorphic brain regions in male rats: the anteroventral periventricular nucleus of the hypothalamus (AVPV) and the sexually dimorphic nucleus of the preoptic area (SDN). In addition to nuclear volumes, we also measured the number of immunopositive calbindin neurons in the SDN and the activational patterns of gonadotropin-releasing hormone (GnRH) neurons, a neuronal population that is functionally linked to the AVPV. In rats, exposure of the neonatal male brain to endogenous estrogen, aromatized from testicular testosterone, is essential for the proper sexual differentiation of these endpoints. Thus, we hypothesized that exposure to BIS and GEN during this critical period could disrupt brain sexual differentiation. Animals were given four subcutaneous injections of sesame oil (control), 250 microg GEN, or 250 microg BIS at 12 h intervals over postnatal days (PND) 1 and 2, gonadectomized on PND 85, and treated sequentially with estrogen and progesterone to stimulate Fos expression in GnRH neurons, a marker for their activation. A cohort of age-matched ovariectomized (OVX) females that were given the same hormone treatment in adulthood served as a positive control group. SDN volume was unchanged by treatment, but the number of calbindin neurons in the SDN was significantly increased by both BIS and GEN. GEN, but not BIS, demasculinized male AVPV volume, but patterns of GnRH neuronal activation were not affected by either compound. These results suggest that acute exposure to EACs during a critical developmental period can independently alter nuclear volumes of sexually dimorphic nuclei and their phenotypic profiles in a region specific manner.

Alterations in spatial learning and memory after forced exercise

Exercise has been shown to influence learning and memory. Most studies were performed with a voluntary running paradigm (e.g. running wheel) in mice. However, such effects of exercise on learning and memory are less well demonstrated using a forced running paradigm (e.g. treadmill). The present study was designed to examine the effects of 12 weeks of forced treadmill running on learning and memory performance in rats. We have previously shown that forced running resulted in qualitative and quantitative changes in the cholinergic neurons of the horizontal diagonal band of Broca (HDB) in the septum. This study was conducted in order to determine whether or not these changes occur simultaneously with enhanced learning and memory. The one-day version of the Morris water maze (MWM) test [Frick, K.M., Stillner, E.T., Berger-Sweeney, J., 2000. Mice are not little rats: species differences in a one-day water maze task. NeuroReport 11, 3461-3465] was used to test spatial learning and memory after the exercise period. Our data showed that runners displayed better spatial learning and memory when compared to nonrunners. This was evidently shown by a reduction in the time required for spatial acquisition (p<0.05) and superior probe trial performance (p<0.05). A shorter distance swam by the runners also suggested improved learning over the nonrunners (p<0.05). In an attempt to revalidate our earlier quantitative results, we used design-based stereology (DBS) to estimate the number of cholinergic neuronal profile population in the medial septum and diagonal band (MSDB). We confirmed that forced running increased the cholinergic neuronal profile subpopulation in the HDB (Coefficient of Error<0.2). Taken together, these results indicate that forced exercise could influence learning and memory with a concomitant increase in the number of cholinergic neurons in the HDB.

Stereological methods to assess tissue response for tissue-engineered scaffolds

The stereological approach can provide an objective unbiased assessment of structural change in biological systems. In this review, we elucidate the basic principles of stereology and their implementation in the analysis of tissue response to tissue-engineering scaffolds. A brief outline of tissue response parameters that can be estimated using stereological approach is included. The focus is on frequently quantified parameters in tissue response, such as host tissue infiltration, inflammatory cell numbers, angiogenesis, fibrous tissue thickness, areas of calcification, and/or necrosis, among others. Special consideration is given to sampling techniques and how these techniques can influence the reliability of the obtained results as well as minimizing potential sources of bias. These basic principles are illustrated with practical examples, where measurements are performed and estimations calculated using conventional stereological techniques. As the next generation of biomaterials continue to be developed, it is essential that researchers develop a rigorous and unbiased method of performance quantification.

Cortical anastomotic veins occlusion in the rat including the assessment of cerebral swelling

A rat model composed of the sacrifice of the anterior and posterior cortical anastomotic veins by microsurgical techniques was used for the assessment of brain swelling. Twenty male, 15-week-old Sprague-Dawley rats were used in this animal experiment. Small burr-holes were made over the anterior (the intersection of the line drawn from the posterior border of the orbital rim and the line drawn along the para-midline to the superior sagittal suture) and posterior (inferior point of the posterior end of the zygomatic arch) anastomotic veins. After performing a final inspection and describing the venous vessels, they were sacrificed using bipolar coagulation technique and micro-scissors. Specimens were evaluated using histopathological approach, albumin immunostaining technique and a stereological method. Hemispheric swelling, midline shift, brain oedema, subcortical petechial haemorrhagia, ischemia and necrosis were histopathological findings observed in this experimental study. The albumin immunostaining study demonstrated disrupted areas of the blood-brain barrier in the operated hemisphere. Stereological volumetric analysis revealed an 8% brain swelling in the operated hemispheres compared with unoperated ones. Our results suggest that the sacrifice of the anterior and posterior anastomotic veins may be used as an experimental rat model in the evaluation of brain damage and swelling caused by the occlusion of the venous anastomotic outflow.

Associative Pavlovian conditioning leads to an increase in spinophilin‐immunoreactive dendritic spines in the lateral amygdala

Changes in dendritic spine number and shape are believed to reflect structural plasticity consequent to learning. Previous studies have strongly suggested that the dorsal subnucleus of the lateral amygdala is an important site of physiological plasticity in Pavlovian fear conditioning. In the present study, we examined the effect of auditory fear conditioning on dendritic spine numbers in the dorsal subnucleus of the lateral amygdala using an immunolabelling procedure to visualize the spine-associated protein spinophilin. Associatively conditioned rats that received paired tone and shock presentations had 35% more total spinophilin-immunoreactive spines than animals that had unpaired stimulation, consistent with the idea that changes in the number of dendritic spines occur during learning and account in part for memory.

Effects of nicotine exposure during prenatal or perinatal period on cell numbers in adult rat hippocampus and cerebellum: a stereology study

Smoking during pregnancy poses a potential risk to unborn children. The present study examined the long-term effects of early nicotine exposure on the number of pyramidal and granule cells in the hippocampus, and Purkinje cells in the cerebellar vermis. The loss of neurons is the most severe form of brain injury with significant functional implications. In this study, rats were exposed to nicotine during either the prenatal (PRE) period or both the prenatal and early postnatal (PERI) period. It was hypothesized that nicotine treatment would result in long-term decreases in neuronal numbers, and that PERI treatment would be more detrimental to these cell populations than the PRE treatment. The results showed that neither PRE nor PERI nicotine exposure reduces the numbers of pyramidal, granule or Purkinje cells. Neither the regions where these cells reside, nor the cell densities were affected by nicotine. Although no significant cell loss was observed, the current nicotine exposure regimens may lead to alterations in cellular functions or cytoarchitectures. The present results in conjunction with previous reports showing significant cell loss from nicotine exposure during the brain growth spurt suggest that "patch-like" nicotine exposure during prenatal period may alter the sensitivity or the responsiveness of the developing brain to the injurious effects of nicotine during the most vulnerable stage of brain development - the brain growth spurt. Furthermore, the current stereology cell counting results are not in agreement with some reports in the literature, and this discrepancy may simply be a function of different cell counting techniques used.

Statistical parametric mapping of immunopositive cell density

We developed a new method for comparing immunopositive cell densities across groups of animals and creating statistical parametric maps on standardized sections. As an example, we compared Iba-1 (microglial marker) positive cell densities in rats with (n=6) and without (n=6) unilateral injection of 1-methyl-4-phenylpyridinium salt (MPP+). Immunopositive cells were automatically counted in each animal over a coronal section in the midbrain (bregma -5.9 mm) and a positive cell density map was created for each animal. After the positive cell density map was normalized to a template section from an atlas, positive cell densities of the two groups were compared in each pixel over the section and a statistical parameter (p-value from t-test) was mapped on each pixel. We were able to detect significant increases of microglias in the side of MPP+ injection not only in the substantia nigra pars compacta but also in adjacent white matter. We also applied the same analysis to tyrosine hydroxylase stained sections and detected significant decreases of dopamine neurons in the side of MPP+ injection. The new method was proven to be useful for detecting significant changes of cell densities over the entire area of immunostained sections.

Myostatin inhibition slows muscle atrophy in rodent models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease leading to motor neuron cell death, but recent studies suggest that non-neuronal cells may contribute to the pathological mechanisms involved. Myostatin is a negative regulator of muscle growth whose function can be inhibited using neutralizing antibodies. In this study, we used transgenic mouse and rat models of ALS to test whether treatment with anti-myostatin antibody slows muscle atrophy, motor neuron loss, or disease onset and progression. Significant increases in muscle mass and strength were observed in myostatin-antibody-treated SOD1(G93A) mice and rats prior to disease onset and during early-stage disease. By late stage disease, only diaphragm muscle remained significantly different in treated animals in comparison to untreated controls. Myostatin inhibition did not delay disease onset nor extend survival in either the SOD1(G93A) mouse or rat. Together, these results indicate that inhibition of myostatin does not protect against the onset and progression of motor neuron degenerative disease. However, the preservation of skeletal muscle during early-stage disease and improved diaphragm morphology and function maintained through late stage disease suggest that anti-myostatin therapy may promote some improved muscle function in ALS.

Normoxic resuscitation after cardiac arrest protects against hippocampal oxidative stress, metabolic dysfunction, and neuronal death

Resuscitation and prolonged ventilation using 100% oxygen after cardiac arrest is standard clinical practice despite evidence from animal models indicating that neurologic outcome is improved using normoxic compared with hyperoxic resuscitation. This study tested the hypothesis that normoxic ventilation during the first hour after cardiac arrest in dogs protects against prelethal oxidative stress to proteins, loss of the critical metabolic enzyme pyruvate dehydrogenase complex (PDHC), and minimizes subsequent neuronal death in the hippocampus. Anesthetized beagles underwent 10 mins ventricular fibrillation cardiac arrest, followed by defibrillation and ventilation with either 21% or 100% O2. At 1 h after resuscitation, the ventilator was adjusted to maintain normal blood gas levels in both groups. Brains were perfusion-fixed at 2 h reperfusion and used for immunohistochemical measurements of hippocampal nitrotyrosine, a product of protein oxidation, and the E1alpha subunit of PDHC. In hyperoxic dogs, PDHC immunostaining diminished by approximately 90% compared with sham-operated dogs, while staining in normoxic animals was not significantly different from nonischemic dogs. Protein nitration in the hippocampal neurons of hyperoxic animals was 2-3 times greater than either sham-operated or normoxic resuscitated animals at 2 h reperfusion. Stereologic quantification of neuronal death at 24 h reperfusion showed a 40% reduction using normoxic compared with hyperoxic resuscitation. These results indicate that postischemic hyperoxic ventilation promotes oxidative stress that exacerbates prelethal loss of pyruvate dehydrogenase and delayed hippocampal neuronal cell death. Moreover, these findings indicate the need for clinical trials comparing the effects of different ventilatory oxygen levels on neurologic outcome after cardiac arrest.

Cytokine-induced activation of glial cells in the mouse brain is enhanced at an advanced age

Numerous neurological diseases which include neuroinflammatory components exhibit an age-related prevalence. The aging process is characterized by an increase of inflammatory mediators both systemically and in the brain, which may prime glial cells. However, little information is available on age-related changes in the glial response of the healthy aging brain to an inflammatory challenge. This problem was here examined using a mixture of the proinflammatory cytokines interferon-gamma and tumor necrosis factor-alpha, which was injected intracerebroventricularly in young (2-3.5 months), middle-aged (10-11 months) and aged (18-21 months) mice. Vehicle (phosphate-buffered saline) was used as control. After a survival of 1 or 2 days (all age groups) or 4 days (young and middle-aged animals), immunohistochemically labeled astrocytes and microglia were investigated both qualitatively and quantitatively. In all age groups, astrocytes were markedly activated in periventricular as well as in deeper brain regions 2 days following cytokine treatment, whereas microglia activation was already evident at 24 h. Interestingly, cytokine-induced activation of both astrocytes and microglia was significantly more marked in the brain of aged animals, in which it included numerous ameboid microglia, than of younger age groups. Moderate astrocytic activation was also seen in the hippocampal CA1 field of vehicle-treated aged mice. FluoroJade B histochemistry and the terminal deoxynucleotidyl transferase-mediated UTP nick-end labeling technique, performed at 2 days after cytokine administration, did not reveal ongoing cell death phenomena in young or aged animals. This indicated that glial cell changes were not secondary to neuronal death. Altogether, the findings demonstrate for the first time enhanced activation of glial cells in the old brain, compared with young and middle-aged subjects, in response to cytokine exposure. Interestingly, the results also suggest that such enhancement does not develop gradually since youth, but appears characterized by relatively late onset.

Diversity of laminar connections linking periarcuate and lateral intraparietal areas depends on cortical structure

Lateral prefrontal and intraparietal cortices have strong connectional and functional associations but it is unclear how their common visuomotor, perceptual and working memory functions arise. The hierarchical scheme of cortical processing assumes that prefrontal cortex issues 'feedback' projections to parietal cortex. However, the architectonic heterogeneity of these cortices raises the question of whether distinct areas have laminar-specific interconnections underlying their complex functional relationship. Using quantitative procedures, we showed that laminar-specific connections between distinct prefrontal (areas 46 and 8) and lateral intraparietal (LIPv, LIPd and 7a) areas in Macaca mulatta, studied with neural tracers, varied systematically according to rules determined by the laminar architecture of the linked areas. We found that axons from areas 46 and rostral 8 terminated heavily in layers I-III of all intraparietal areas, as did caudal area 8 to area LIPv, suggesting 'feedback' communication. However, contrary to previous assumptions, axons from caudal area 8 terminated mostly in layers IV-V of LIPd and 7a, suggesting 'feedforward' communication. These laminar patterns of connections were highly correlated with consistent differences in neuronal density between linked areas. When neuronal density in a prefrontal origin was lower than in the intraparietal destination, most terminations were found in layer I with a concomitant decrease in layer IV. The opposite occurred when the prefrontal origin had a higher neuronal density than the target. These findings indicate that the neuronal density of linked areas can reliably predict their laminar connections and may form the basis of understanding the functional complexity of prefrontal-intraparietal interactions in cognition.

Glial fibrillary acidic protein and related glial proteins as biomarkers of neurotoxicity

A variety of '-omic' technologies are being increasingly applied in preclinical safety assessments. Such approaches, however, have not been implemented in neurotoxicity safety evaluations. Current regulatory guidelines for assessing neurotoxicity emphasise reliance on traditional histopathological stains and behavioural testing batteries. Although these methods may be sufficient to detect some neurotoxic effects, they lack both the sensitivity and specificity required for broad-scale neurotoxicity screening. The glial reaction to nervous system damage, often termed gliosis, represents a hallmark of all types of nervous system injury. As such, the development and implementation of gliosis biomarkers represents a broadly applicable approach for neurotoxicity safety assessment. Using a panel of known neurotoxic agents, the authors have shown that the astroglial protein, glial fibrillary acidic protein (GFAP), can serve as one such biomarker of neurotoxicity. Qualitative and quantitative analysis of GFAP has shown this biomarker to be a sensitive and specific indicator of the neurotoxic condition. The implementation of GFAP and related glial biomarkers in neurotoxicity screens may serve as the basis for further development of molecular signatures predictive of adverse effects on the nervous system.

Selective striatal neuron loss and alterations in behavior correlate with impaired striatal function in Huntington's disease transgenic rats

Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by selective striatal neuron loss and motor, cognitive and affective disturbances. The present study aimed to test the hypothesis of adult-onset neuron loss in striatum and frontal cortical layer V as well as alterations in behavior pointing to impaired striatal function in a recently developed transgenic rat model of HD (tgHD rats) exhibiting enlarged ventricles, striatal atrophy and pycnotic pyramidal cells in frontal cortical layer V. High-precision design-based stereological analysis revealed a reduced mean total number of neurons in the striatum but not in frontal cortical layer V of 12-month-old tgHD rats compared with age-matched wild-type controls. No alterations in mean total numbers of striatal neurons were found in 6-month-old animals. Testing 14-month-old animals in a choice reaction time task indicated impaired striatal function of tgHD rats compared with controls.

HIV-1 Tat and opiate-induced changes in astrocytes promote chemotaxis of microglia through the expression of MCP-1 and alternative chemokines

Opiates exacerbate human immunodeficiency virus type 1 (HIV-1) Tat(1-72)-induced release of key proinflammatory cytokines by astrocytes, which may accelerate HIV neuropathogenesis in opiate abusers. The release of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in particular, is potentiated by opiate-HIV Tat interactions in vitro. Although MCP-1 draws monocytes/macrophages to sites of CNS infection, and activated monocytes/microglia release factors that can damage bystander neurons, the role of MCP-1 in neuro-acquired immunodeficiency syndrome (neuroAIDS) progression in opiate abusers, or nonabusers, is uncertain. Using a chemotaxis assay, N9 microglial cell migration was found to be significantly greater in conditioned medium from mouse striatal astrocytes exposed to morphine and/or Tat(1-72) than in vehicle-, mu-opioid receptor (MOR) antagonist-, or inactive, mutant Tat(delta31-61)-treated controls. Conditioned medium from astrocytes treated with morphine and Tat caused the greatest increase in motility. The response was attenuated using conditioned medium immunoneutralized with MCP-1 antibodies, or medium from MCP-1(-/-) astrocytes. In the presence of morphine (time-release, subcutaneous implant), intrastriatal Tat increased the proportion of neural cells that were astroglia and F4/80+ macrophages at 7 days post-injection. This was not seen after treatment with Tat alone, or with morphine plus inactive Tat(delta31-61) or naltrexone. Glia displayed increased MOR and MCP-1 immunoreactivity after morphine and/or Tat exposure. The findings indicate that MCP-1 underlies most of the response of microglia, suggesting that one way in which opiates exacerbate neuroAIDS is by increasing astroglial-derived proinflammatory chemokines at focal sites of CNS infection and promoting macrophage entry and local microglial activation. Importantly, increased glial expression of MOR can trigger an opiate-driven amplification/positive feedback of MCP-1 production and inflammation.

Reduced hippocampal volume in drug-free depressed patients

A number of studies have used magnetic resonance imaging to examine the volumetric differences in temporal lobe structures especially the hippocampus in patients suffering from major depressive disorder (MDD). Although some studies reported lower hippocampal volume, others did not. It is proposed that the inconsistency among studies may be due to the heterogeneity of patients and antidepressant treatment during scanning. In this study, we aimed to evaluate the hippocampus in drug-free patients. Twenty-four patients (6 males and 18 females) diagnosed as having MDD according to the DSM-IV criteria and 24 healthy controls (6 males and 18 females) were included in the study. Eleven of the patients had their first mood episode and were drug-naïve. Other patients were drug-free for at least 4 weeks. The Hamilton depression rating scale (HAM-D) assessed the severity of depression. Magnetic resonance imaging was performed on a 1.5-T MR unit. The Cavalieri method of modern design stereology in conjunction with point counting was used to estimate hippocampal volume. The data were evaluated by a repeated measure of ANOVA and the intracranial volume was taken as a covariate. A significant hippocampal volume difference was observed between the patients and healthy controls (F=4.43, df=1.45, P<0.05); however, laterality had no effect on the volumes (F=0.03, df=1.45, P>0.05). The left hippocampus of patients was significantly lower than those of controls (t=1.98, df=46, P<0.05). Correlation analysis showed a correlation between HAM-D scores and the right hippocampal volume. The results of this study indicate that hippocampus volume is reduced in depressed patients especially in the left side. This finding in the drug-free depressed outpatients without a history of alcohol dependence supports previous studies that have reported lower hippocampal volume.

Subpopulations of motor and sensory neurons respond differently to brain-derived neurotrophic factor depending on the presence of the skeletal muscle

The aim of our study was to assess the ability of brain-derived neurotrophic factor (BDNF) to rescue motor and sensory neurons from programmed cell death. It is clearly demonstrated that the administration of a single injection of a putative neurotrophic factor to mouse embryos in utero on embryonic day (E) 14.5 is sufficient to significantly reduce the death of motor neurons when assessed on E18.5. However, the trophic requirements of somatic neurons have not been unequivocally determined in a mammalian species in vivo. Indeed, the unexpectedly high numbers of surviving neurons observed in neurotrophin and tyrosine kinase receptor knockout mice are probably the consequence of functional redundancy between the neurotrophins and their receptors. We studied spinal cord and facial motor nucleus neurons and proprioceptive neurons in the dorsal root ganglion and mesencephalic nucleus. The action of BDNF was assessed in wild-type fetuses to gain insight into its ability to rescue neurons from naturally occurring programmed cell death. In addition, we used Myf5(-/-):MyoD(-/-) embryos, which completely lack skeletal musculature, to assess the ability of BDNF to rescue neurons from excessively occurring programmed cell death. We found that BDNF differentially rescued neurons from naturally vs. excessively occurring cell death and that its ability to do so varied among neuronal subpopulations.

Two distinct events, section compression and loss of particles (“lost caps”), contribute toz-axis distortion and bias in optical disector counting

Deformation of tissue sections in the z-axis can bias optical disector counting. When samples of particle densities are not representative for the entire tissue section, significant bias of estimated numbers can result. To assess the occurrence, prevalence, extent, sequence of events, and causes of z-axis distortion, the distribution of neuronal nucleoli in thick paraffin and vibratome sections was determined in chicken, rodent, and human brain tissues. When positions of neuronal nucleoli were measured in the z-axis, nucleoli were more frequent at the surfaces (bottom and top) of tissue sections than in the core. This nonlinear z-axis distribution was not lab-, equipment-, or investigator-specific, and was independent of age, fixation quality, coverslipping medium, or paraffin melting temperature, but in paraffin sections, was highly correlated with the tilt of the knife (cutting) angle. Manipulation of subsequent tissue processing steps revealed that two events contribute to z-axis distortion. Initially, a higher density of particles results at surfaces after sectioning, apparently due to section compression. Subsequently, particles can be lost to varying degrees from surfaces during floating or staining and dehydration, resulting in "lost caps." These results may explain different degrees of z-axis distortion between different types of sections and different labs, and reinforce the importance of checking z-axis distributions as a "quality control" prior to selection of guard zones in optical disector counting. Indirect approaches to assess section quality, such as resectioning in a perpendicular plane, yield additional artifacts, and should be replaced by a direct quantitative measurement of z-axis distribution of particles.

Enriched environment induces cellular plasticity in the adult substantia nigra and improves motor behavior function in the 6-OHDA rat model of Parkinson's disease

The adult substantia nigra bears the capacity to generate new neural cells throughout adulthood. The mechanisms of cellular plasticity in this brain region remain unknown. In the adult dentate gyrus, dopamine was suggested to be one of the key players in neurogenesis. We therefore investigated nigral cellular plasticity in the 6-OHDA rat model of Parkinson's disease. The absolute numbers of newborn cells in the SN were not affected by dopamine depletion. Interestingly, we found a specific downregulation of generation of newborn nigral astrocytic cells. As enriched environment with physical activity are robust inducers of neuro- and gliogenesis in the adult DG, we investigated the role of these physiological stimuli in nigral cellular plasticity and in motor behavior of 6-OHDA lesioned rats. We describe a significant increase in numbers of newborn NG2-positive and GFAP-positive cells in the SN. Moreover, 6-OHDA lesioned animals living in enriched environment with physical activity for 7 weeks showed improved motor behavior compared to controls under standard conditions. Thus, physiological neurogenic and gliogenic stimuli induce significant microenvironmental changes in the adult SN and improve motor behavior in the 6-OHDA lesion model of PD.

Histamine-immunoreactive neurons in the mouse and rat suprachiasmatic nucleus

Among the well-established roles of the neurotransmitter histamine (HA) is that as a regulator of the sleep-wake cycle, which early gained HA a reputation as a 'waking substance'. The tuberomammillary nucleus (TMN) of the posterior hypothalamus, which contains the sole source of neuronal HA in the brain, is reciprocally connected to the suprachiasmatic nucleus (SCN) which, in turn, is best known as the pacemaker of circadian rhythms in mammals. We report HA-immunoreactive (-ir) neurons in the mouse and rat SCN that neither display immunoreactivity (-iry) for the HA-synthesizing enzyme histidine decarboxylase (HDC) nor contain HDC mRNA. Further, HA-iry was absent in the SCN of HDC knockout mice, but present in appropriate control animals, indicating that the observed HA-iry is HDC dependent. Experiments with hypothalamic slice cultures and i.c.v. injection of HA suggest that HA in the SCN neurons originates in the TMN and is transported from the TMN along histaminergic fibres known to innervate the SCN. These results could indicate the existence of a hitherto unknown uptake mechanism for HA into neurons. Through HA uptake and, putatively, re-release of the captured HA, these neurons could participate in the HA-mediated effects on the circadian system in concert with direct histaminergic inputs from the TMN to the SCN. The innervation of the SCN by several neurotransmitter systems could provide a way for other systems to affect the HA-containing neuronal cell bodies in the SCN.