Effect of rabies virus infection on the expression of parvalbumin, calbindin and calretinin in mouse cerebral cortex

Some clinical features of rabies and experimental evidence from cell culture and laboratory animals suggest impairment of gabaergic neurotransmission. Several types of gabaergic neurons occur in the cerebral cortex. They can be identified by three neuronal markers: the calcium binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR). Rabies virus spreads throughout the cerebral cortex; however, rabies cytopathic effects on gabaergic neurons are unknown. The expression of calcium-binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR) was studied in the frontal cortex of mice. The effect of gabaergic neurons was evaluated immunohistochemically. The distribution patterns of CaBPs in normal mice and in mice infected with 'fixed' or 'street' rabies virus were compared. PV was found in multipolar neurons located in all cortical layers except layer I, and in pericellular clusters of terminal knobs surrounding the soma of pyramidal neurons. CB-immunoreactivity was distributed in two cortical bands. One was composed of round neurons enclosed by a heavily labeled neuropil; this band corresponds to supragranular layers II and III. The other was a weakly stained band of neuropil which contained scattered multipolar CB-ir neurons; this corresponds to infragranular layers V and VI. The CR-ir neurons were bipolar fusiform cells located in all layers of cortex, but concentrated in layers II and III. A feature common to samples infected with both types of viruses was a more intense immunoreactivity to PV in contrast to normal samples. The infection with 'street' virus did not cause additional changes in the expression of CaBPs. However, the infection with 'fixed' virus produced a remarkable reduction of CB-immunoreactivity demonstrated by the loss of CB-ir neurons and low neuropil stain in the frontal cortex. In addition, the size of CR-ir neurons in the cingulate cortex was decreased.     

Relocalization of a microtubule-anchoring protein,ninein, from the centrosome to dendrites during differentiation of mouse neurons

Microtubules in typical cells form radial arrays with their plus-ends pointing toward the cell periphery. In contrast, microtubules in dendrites of neurons are free from centrosomes and have a unique arrangement in which about half have a polarity with a minus-end distal orientation. Mechanisms for generation and maintenance of the microtubule arrangement in dendrites are not well understood. Here, we examined dendritic localization of a centrosomal protein, ninein, which has microtubule-anchoring and stabilizing functions. Immunohistochemical analysis of developing mouse cerebral and cerebellar cortices showed that ninein is localized at the centrosome in undifferentiated neural precursors. In contrast, ninein was barely detected in migrating neurons, such as those in the intermediate layer of the cerebral cortex and the internal granular layer of the cerebellar cortex. High expression was observed in thick dendrite-bearing neurons such as pyramidal neurons of the cerebral cortex and Purkinje neurons in the cerebellar cortex. Ninein was not detected at the centrosome of these cells, but was diffusely present in cell soma and dendrites. In cultured cortical neurons, ninein formed granular structures in soma and dendrites, being not associated with γ-tubulin. About 60% of these structures showed resistance to detergent and association with microtubules. Our observations suggest that the minus-ends of microtubules may be anchored and stabilized by centrosomal proteins localized in dendrites.     

Intrinsic organization of the medial cerebral cortex of the lizard Lacerta pityusensis: A golgi study

The morphology of cells and the organization of axons were studied in Golgi-Colonnier and toluidine blue stained preparations from the medial cerebral cortex of the lizard Lacerta pityusensis. In the medial cortex, six strata were distinguished between the superficial glial membrane and the ependyma. Strata I and II formed the outer plexiform layer, stratum III formed the cellular layer, and strata IV go VI the inner plexiform layer. The outer plexiform layer contained smooth bipolar neurons; their dendrites were oriented anteroposteriorly and their axons were directed towards the posterior zone of the brain. Five neuronal types were observed in the cellular layer. The spinous pyramidal neurons had well-developed apical dendrites and poorly developed basal ones. Their axons entered the inner plexiform layer and gave off collaterals oriented anteroposteriorly. The small, sparsely spinous pyramidal neurons had poorly developed dendrites and their axons entered the inner plexiform layer. The spinous bitufted neurons had well-developed apical and basal dendritic tufts. Their axons gave off collaterals that reached the outer and inner plexiform layers of both the dorsomedial and dorsal cortices. The sparsely spinous horizontal neurons had dendrites restricted to the outer plexiform layer. Their axons entered the inner plexiform layer. The sparsely spinous, multipolar neurons had their soma close to stratum IV and their axons entered the outer plexiform layer. In stratum V of the inner plexiform layer were large, spiny polymorphic neurons; they had dendrites with long spines, and their axons reached the cellular layer. On the basis of these results, we have subdivided the medial cortex into two subregions: the superficial region, which contains the neurons of the cellular layer and their dendritic domains, and the deep region, strata V and VI, which contains the large, spiny polymorphic neurons. The neurons in the medial cortex of these lizards resembles those in the area dentata of mammals. On this basis, the superficial region may be compared to the dentate gyrus and the deep region to the hilar region of the hippocampus of mammals.     

Rabies virus entry into cultured rat hippo campalneurons

Rabies virus entry into cultured hippocampal neurons was investigated by immunofluorescence and electron microscopy. Hippocampal neurons were susceptible to rabies virus infection and became filled with viral antigen 1 day after infection. Infection was inhibited by the lysosomotropic agents chloroquine and ammonium chloride. To study entry, neurons were adsorbed with rabies virus at 4°C and warmed to 37°C for short periods of time prior to fixation and localization of viral antigen by immunofluorescence microscopy. By 5 min at 37°C, viral antigen was localized to puncta in the cell body and dendrites and in synapses along dendrites. Little viral antigen was present in axons. Cells adsorbed with rabies virus were incubated with tracers for early endosomes. The endocytic tracers or markers Lucifer Yellow, transferrin receptor, dextran, and wheat germ agglutinin co-localized with rabies virus, indicating that rabies virus enters an endosome compartment shortly after uptake. Rabies virus also co-localized with LysoTracker Red, an acidotropic probe, indicating that some of the virus-containing endosomes are acidified. Rabies virus also co-localized with synapsin I, a synaptic vesicle marker, in nerve terminals but did not co-localize with lysosomal glycoprotein. By electron microscopy, after adsorption of virus and warming for 10 min, virus particles were present in coated pits, coated vesicles, and vacuolar membrane compartments in processes and axon terminals. It is concluded that rabies virus enters the somatodendritic domain and axon terminals of cultured hippocampal neurons by adsorptive endocytosis and is located in endosomes shortly after uptake.     

Apoptosis plays an important role in experimental rabies virus infection.

Cultured rat prostatic adenocarcinoma (AT3) cells infected with the challenge virus standard (CVS) strain of fixed rabies virus showed characteristic morphologic features of apoptosis, evidence of oligonucleosomal DNA fragmentation, and expression of the Bax protein. CVS-infected Bcl-2-transfected AT3 cells did not demonstrate these features. Adult ICR mice inoculated intracerebrally with CVS showed morphologic changes of apoptosis, DNA fragmentation, and increased Bax expression in neurons, with changes most marked in the hippocampus and cerebral cortex. Ultrastructurally, some neurons demonstrated morphologic features more typical of necrosis. These studies provide evidence that apoptosis plays an important role in the pathogenesis of rabies virus infection.     

Widespread distribution of the major polypeptide component of MAP 1 (microtubule-associated protein 1) in the nervous system

We prepared a monoclonal antibody to microtubule-associated protein 1 (MAP 1), one of the two major high molecular weight MAP found in microtubules isolated from brain tissue. We found that MAP 1 can be resolved by SDS PAGE into three electrophoretic bands, which we have designated MAP 1A, MAP 1B, and MAP 1C in order of increasing electrophoretic mobility. Our antibody recognized exclusively MAP 1A, the most abundant and largest MAP 1 polypeptide. To determine the distribution of MAP 1A in nervous system tissues and cells, we examined tissue sections from rat brain and spinal cord, as well as primary cultures of newborn rat brain by immunofluorescence microscopy. Anti-MAP 1A stained white matter and gray matter regions, while a polyclonal anti-MAP 2 antibody previously prepared in this laboratory stained only gray matter. This confirmed our earlier biochemical results, which indicated that MAP 1 is more uniformly distributed in brain tissue than MAP 2 (Vallee, R.B., 1982, J. Cell Biol., 92:435-442). To determine the identity of cells and cellular processes immunoreactive with anti-MAP 1A, we examined a variety of brain and spinal cord regions. Fibrous staining of white matter by anti-MAP 1A was generally observed. This was due in part to immunoreactivity of axons, as judged by examination of axonal fiber tracts in the cerebral cortex and of large myelinated axons in the spinal cord and in spinal nerve roots. Cells with the morphology of oligodendrocytes were brightly labeled in white matter. Intense staining of Purkinje cell dendrites in the cerebellar cortex and of the apical dendrites of pyramidal cells in the cerebral cortex was observed. By double-labeling with antibodies to MAP 1A and MAP 2, the presence of both MAP in identical dendrites and neuronal perikarya was found. In primary brain cell cultures anti-MAP 2 stained predominantly cells of neuronal morphology. In contrast, anti-MAP 1A stained nearly all cells. Included among these were neurons, oligodendrocytes and astrocytes as determined by double-labeling with anti-MAP 1A in combination with antibody to MAP 2, myelin basic protein or glial fibrillary acidic protein, respectively. These results indicate that in contrast to MAP 2, which is specifically enriched in dendrites and perikarya of neurons, MAP 1A is widely distributed in the nervous system.     

The anatomy of the cerebral cortex of the echidna (Tachyglossus aculeatus)

The cerebral cortex of the echidna is notable for its extensive folding and the positioning of major functional areas towards its caudal extremity. The gyrification of the echidna cortex is comparable in magnitude to prosimians and cortical thickness and neuronal density are similar to that seen in rodents and carnivores. On the other hand, many pyramidal neurons in the cerebral cortex of the echidna are atypical with inverted somata and short or branching apical dendrites. All other broad classes of neurons noted in therian cortex are also present in the echidna, suggesting that the major classes of cortical neurons evolved prior to the divergence of proto- and eutherian lineages. Dendritic spine density on dendrites of echidna pyramidal neurons in somatosensory cortex and apical dendrites of motor cortex pyramidal neurons is lower than that found in eutheria. On the other hand, synaptic morphology, density and distribution in somatosensory cortex are similar to that in eutheria. In summary, although the echidna cerebral cortex displays some structural features, which may limit its functional capacities (e.g. lower spine density on pyramidal neurons), in most structural parameters (e.g. gyrification, cortical area and thickness, neuronal density and types, synaptic morphology and density), it is comparable to eutheria.     

Changes in the dendrite ultrastructure of the cerebral cortex neurons in human tumors located in the hypothalamo-hypophyseal area

By means of electron microscopy method of bioptic material structure of the neuronal islets of the cerebral cortex has been studied in 5 persons with benign tumors that immediately effect the hypothalamus. Certain changes in ultrastructure of dendrites are revealed according to the light and dark types, as well as axons, degenerating according to the dark type. The greatest changes, including degeneration according to the dark type, undergo small branches of the dendrites. Similar pictures reflect, evidently, reduction of the dendritic tree in slightly changed cortical neurons, connected with breaking of trophic influences in the hypothalamus, evoked in it by the tumor.     

The organization of double bouquet cells in monkey striate cortex

In previous publications we proposed a model of cortical organization in which the pyramidal cells of the cerebral cortex are organized into modules. The modules are centred around the clusters of apical dendrites that originate from the layer 5 pyramidal cells. In monkey striate cortex such modules have an average diameter of 23 μm and the outputs originating from the modules are contained in the vertical bundles of myelinated axons that traverse the deeper layers of the cortex. The present study is concerned with how the double bouquet cells in layer 2/3 of striate cortex relate to these pyramidal cell modules. The double bouquet cells are visualized with an antibody to calbindin, and it has been shown that their vertically oriented axons, or horse tails, are arranged in a regular array, such that there is one horse tail per pyramidal cell module. Within layer 2/3 the double bouquet cell axons run alongside the apical dendritic clusters, while in layer 4C they are closely associated with the myelinated axon bundles. However, the apical dendrites are not the principal targets of the double bouquet cell axons. Most of the neuronal elements post-synaptic to them are the shafts of small dendrites (60%) and dendritic spines, with which they form symmetric synapses. This regular arrangement of the axons of the double-bouquet cells and their relationship to the components of the pyramidal cells modules supports the concept that there are basic, repeating neuronal circuits in the cortex.     

Localisation of Formyl-Peptide Receptor 2 in the Rat Central Nervous System and Its Role in Axonal and Dendritic Outgrowth

Arachidonic acid and docosahexaenoic acid (DHA) released by the action of phospholipases A₂ (PLA₂) on membrane phospholipids may be metabolized by lipoxygenases to the anti-inflammatory mediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), and these can bind to a common receptor, formyl-peptide receptor 2 (FPR2). The contribution of this receptor to axonal or dendritic outgrowth is unknown. The present study was carried out to elucidate the distribution of FPR2 in the rat CNS and its role in outgrowth of neuronal processes. FPR2 mRNA expression was greatest in the brainstem, followed by the spinal cord, thalamus/hypothalamus, cerebral neocortex, hippocampus, cerebellum and striatum. The brainstem and spinal cord also contained high levels of FPR2 protein. The cerebral neocortex was moderately immunolabelled for FPR2, with staining mostly present as puncta in the neuropil. Dentate granule neurons and their axons (mossy fibres) in the hippocampus were very densely labelled. The cerebellar cortex was lightly stained, but the deep cerebellar nuclei, inferior olivary nucleus, vestibular nuclei, spinal trigeminal nucleus and dorsal horn of the spinal cord were densely labelled. Electron microscopy of the prefrontal cortex showed FPR2 immunolabel mostly in immature axon terminals or ‘pre-terminals’, that did not form synapses with dendrites. Treatment of primary hippocampal neurons with the FPR2 inhibitors, PBP10 or WRW4, resulted in reduced lengths of axons and dendrites. The CNS distribution of FPR2 suggests important functions in learning and memory, balance and nociception. This might be due to an effect of FPR2 in mediating arachidonic acid/LXA4 or DHA/RvD1-induced axonal or dendritic outgrowth.     

Interactions between entorhinal axons and target hippocampal neurons: a role for glutamate in the development of hippocampal circuitry

A coculture system consisting of input axons from entorhinal cortex explants and target hippocampal pyramidal neurons was used to demonstrate that glutamate, released spontaneously from afferent axons, can influence both dendritic geometry of target neurons and formation of presumptive synaptic sites. Dendritic outgrowth was reduced in hippocampal neurons growing on entorhinal axons when compared with neurons growing off the axons. Presumptive presynaptic sites were observed in association with hippocampal neuron dendrites and somas. HPLC analysis showed that glutamate was released from the explants in an activity- and Ca2(+)-dependent manner. The general glutamate receptor antagonist D-glutamylglycine significantly increased dendritic outgrowth in pyramidal neurons associated with entorhinal axons and reduced presumptive presynaptic sites. Tetrodotoxin and reduction of extracellular Ca2+ also promoted dendritic outgrowth and reduced the formation of presumptive synaptic sites. The results suggest that the neurotransmitter glutamate may play important roles in the development of hippocampal circuitry.     

Heterogeneity of axon terminals expressing VGLUT1 in the cerebral neocortex

Using immunocytochemical techniques and confocal microscopy we have studied the localization of the vesicular glutamate transporters (VGLUTs) 1 and 2 in the mammalian cerebral cortex. The cardinal observations gathered to date can be summarized as follows: 1) Many VGLUT1-positive puncta coexpressing synaptophysin-1 outline pyramidal cell somata and proximal dendrites; of these, a sizeable fraction coexpress VGAT, the vesicular transporter for GABA; 2) VGLUT2-positive puncta are also present in layers II-III and some of them coexpress VGLUTI. These findings suggest that in the cerebral cortex of adult rats axon terminals expressing VGLUT1 are heterogeneous.     

In vivo transduction of central neurons using recombinant Sindbis virus: Golgi-like labeling of dendrites and axons with membrane-targeted fluorescent proteins.

A new recombinant virus which labeled the infected neurons in a Golgi stain-like fashion was developed. The virus was based on a replication-defective Sindbis virus and was designed to express green fluorescent protein with a palmitoylation signal (palGFP). When the virus was injected into the ventrobasal thalamic nuclei, many neurons were visualized with the fluorescence of palGFP in the injection site. The labeling was enhanced by immunocytochemical staining with an antibody to green fluorescent protein to show the entire configuration of the dendrites. Thalamocortical axons of the infected neurons were also intensely immunostained in the somatosensory cortex. In contrast to palGFP, when DsRed with the same palmitoylation signal (palDsRed) was introduced into neurons with the Sindbis virus, palDsRed neither visualized the infected neurons in a Golgi stain-like manner nor stained projecting axons in the cerebral cortex. The palDsRed appeared to be aggregated or accumulated in some organelles in the infected neurons. Anterograde labeling with palGFP Sindbis virus was very intense, not only in thalamocortical neurons but also in callosal, striatonigral, and nigrostriatal neurons. Occasionally there were retrogradely labeled neurons that showed Golgi stain-like images. These results indicate that palGFP Sindbis virus can be used as an excellent anterograde tracer in the central nervous system.     

An electron microscopic study of neuronal development in organotypic cultures of the anlage of the cerebral cortex from a human embryo

Data are provided on cytodifferentiation of the cerebral cortex cultured cells taken from 10-12 week old embryos of man. It is shown that low differentiated neuroblasts well survive in culture for 21 days. Mature granular cells and middle pyramidal neurons are revealed in cultures. The number of morphological criteria may testify to the maturity of neurons: the presence of the Nissl substance, differentiation of dendrites and axons; the presence of various types of synapses. The absence of myelinized fibres testifies to the insufficient maturity of the cultures, that is probably associated with employing the low differentiated nervous tissue for cultivation and with insufficient cultivation period.     

Specialized circuits from primary visual cortex to V2 and area MT

Primary visual cortex recombines inputs from magnocellular (M) and parvocellular (P) streams to create functionally specialized outputs. Understanding these input-output relationships is complicated by the fact that layer 4B, which provides outputs to dorsal visual areas, contains multiple cell types. Using a modified rabies virus that expresses green fluorescent protein, we show that layer 4B neurons projecting to MT are a majority spiny stellate, whereas those projecting to V2 are overwhelmingly pyramidal. Regardless of cell type, MT-projecting neurons have larger cell bodies, more dendritic length, and are deeper within layer 4B. Furthermore, MT-projecting pyramidal neurons are located preferentially underneath cytochrome oxidase blobs, indicating that MT-projecting neurons of both types restrict their dendrites to M-recipient zones. We conclude that MT-projecting layer 4B neurons are specialized for the fast transmission of information from the M pathway, while V2-projecting neurons are likely to mediate slower computations involving mixed M and P signals.     

Neural recognition molecules CHL1 and NB-3 regulate apical dendrite orientation in the neocortex via PTP alpha

Apical dendrites of pyramidal neurons in the neocortex have a stereotypic orientation that is important for neuronal function. Neural recognition molecule Close Homolog of L1 (CHL1) has been shown to regulate oriented growth of apical dendrites in the mouse caudal cortex. Here we show that CHL1 directly associates with NB-3, a member of the F3/contactin family of neural recognition molecules, and enhances its cell surface expression. Similar to CHL1, NB-3 exhibits high-caudal to low-rostral expression in the deep layer neurons of the neocortex. NB-3-deficient mice show abnormal apical dendrite projections of deep layer pyramidal neurons in the visual cortex. Both CHL1 and NB-3 interact with protein tyrosine phosphatase alpha (PTPalpha) and regulate its activity. Moreover, deep layer pyramidal neurons of PTPalpha-deficient mice develop misoriented, even inverted, apical dendrites. We propose a signaling complex in which PTPalpha mediates CHL1 and NB-3-regulated apical dendrite projection in the developing caudal cortex.     

Noradrenergic enhancement of Ca2+ responses of basal dendrites in layer 5 pyramidal neurons of the prefrontal cortex

Although the excitatory effects of noradrenaline have been thoroughly studied in the central nervous system, there is relatively little known about the adrenergic effects on Ca2+ dynamics of dendrites. In the present study, we imaged basal dendrites of layer 5 pyramidal neurons in the prefrontal cortex using two-photon microscopy. In our experiments noradrenaline, applied in the bath, enhanced excitability of layer 5 pyramidal neurons. The number of evoked action potentials following current injection to the soma increased by 44.7% on average. In the basal dendrites and spines the evoked Ca2+ responses were also markedly enhanced. Noradrenaline-induced effects could be blocked by the beta-adrenergic blocker propranolol. Our data, that activation of the noradrenergic system increases excitability of layer 5 pyramidal neurons via beta-adrenergic receptors and enhances Ca2+ signaling in basal dendrites, suggest a cellular site of action for noradrenaline to improve the integrative capabilities of dendrites.     

Therapy with minocycline aggravates experimental rabies in mice

Minocycline is a tetracycline derivative with antiapoptotic and anti-inflammatory properties, and the drug has been shown to have beneficial effects in a variety of models of neurological disorders. The potentially neuroprotective role of minocycline was assessed in experimental in vitro and in vivo models of rabies virus infection. In this study, 5 nM minocycline did not improve the viability of embryonic mouse cortical and hippocampal neurons infected in vitro with the attenuated SAD-D29 strain of rabies virus, based on assessments using trypan blue exclusion. Two-day-old ICR mice were inoculated in the right hind limb thigh muscle with SAD-D29, and they received daily subcutaneous injections of either 50 mg/kg minocycline or vehicle (phosphate-buffered saline). Infected minocycline-treated mice experienced an earlier onset of neurologic signs and greater mortality (83% versus 50%) than those receiving vehicle (log rank test, P=0.002 and P=0.003, respectively). Immunohistochemical analysis of rabies virus antigen distribution was performed at early time points and in moribund mice. There were greater numbers of infected neurons in the regional brain areas of minocycline-treated mice than in vehicle-treated mice, which was significant in the CA1 region of the hippocampus. There was less apoptosis (P=0.01) and caspase 3 immunostaining (P=0.0008) in the midbrains of mice treated with minocycline than in mice treated with vehicle, consistent with a neuroprotective role of neuronal apoptosis that may have had a mild effect of inhibiting viral spread. Reduced infiltration of CD3+ T cells was observed in the pons/medulla of moribund mice that received minocycline therapy (P=0.008), suggesting that the anti-inflammatory actions of minocycline may intensify the neurologic disease. These findings indicate that minocycline has important detrimental effects in the therapy of experimental rabies. Empirical therapy with minocycline should therefore be approached with caution in cases of human rabies and possibly other viral encephalitides until more experimental data become available.     

GABA immunoreactivity in the human cerebellar cortex: a light and electron microscopical study

The distribution of gamma-aminobutyric acid (GABA) in surgical samples of human cerebellar cortex was studied by light and electron microscope immunocytochemistry using a polyclonal antibody generated in rabbit against GABA coupled to bovine serum albumin with glutaraldehyde. Observations by light microscopy revealed immunostained neuronal bodies and processes as well as axon terminals in all layers of the cerebellar cortex. Perikarya of stellate, basket and Golgi neurons showed evident GABA immunoreactivity. In contrast, perikarya of Purkinje neurons appeared to be negative or weakly positive. Immunoreactive tracts of longitudinally- or obliquely-sectioned neuronal processes and punctate elements, corresponding to axon terminals or cross-sectioned neuronal processes, showed a layer-specific pattern of distribution and were seen on the surface of neuronal bodies, in the neuropil and at microvessel walls. Electron microscope observations mainly focussed on the analysis of GABA-labelled axon terminals and of their relationships with neurons and microvessels. GABA-labelled terminals contained gold particles associated with pleomorphic vesicles and mitochondria and established symmetric synapses with neuronal bodies and dendrites in all cortex layers. GABA-labelled terminals associated with capillaries were seen to contact the perivascular glial processes, basal lamina and endothelial cells and to establish synapses with subendothelial unlabelled axons.     

Increased Uric Acid in the Developing Brain and Spinal Cord Following Cytomegalovirus Infection

Abstract: Tissue concentrations of uric acid were determined in the spinal cord, cerebellum, caudate-putamen, and cerebral cortex of developing mice following intraventricular inoculation with murine cytomegalovirus (MCMV) on postnatal day 10. Transient signs of neurological impairment were observed in MCMV-infected animals beginning on days 13–16 and continuing until days 19–21. At the onset of neurological impairment, uric acid concentrations in tissues from infected animals were 17–60-fold greater than in control animals. On postnatal day 70, 60 days after inoculation and 40 days after resolution of neurological signs, uric acid levels were still two- to threefold greater in infected animals. Histological examination revealed signs of focal ischemia in the cerebral and cerebellar cortices of MCMV-infected mice only at the onset of neurological impairment, with ischemic cell changes in some pyramidal neurons of the cerebral cortex. These results indicate that uric acid may be a sensitive marker of persistent vascular pathology resulting from cytomegalovirus infection of the developing nervous system