Caveats in Transneuronal Tracing with Unmodified Rabies Virus: An Evaluation of Aberrant Results Using a Nearly Perfect Tracing Technique.

Apart from the genetically engineered, modified, strains of rabies virus (RABV), unmodified 'fixed' virus strains of RABV, such as the 'French' subtype of CVS11, are used to examine synaptically connected networks in the brain. This technique has been shown to have all the prerequisite characteristics for ideal tracing as it does not metabolically affect infected neurons within the time span of the experiment, it is transferred transneuronally in one direction only and to all types of neurons presynaptic to the infected neuron, number of transneuronal steps can be precisely controlled by survival time and it is easily detectable with a sensitive technique. Here, using the 'French' CVS 11 subtype of RABV in Wistar rats, we show that some of these characteristics may not be as perfect as previously indicated. Using injection of RABV in hind limb muscles, we show that RABV-infected spinal motoneurons may already show lysis 1 or 2 days after infection. Using longer survival times we were able to establish that Purkinje cells may succumb approximately 3 days after infection. In addition, some neurons seem to resist infection, as we noted that the number of RABV-infected inferior olivary neurons did not progress in the same rate as other infected neurons. Furthermore, in our hands, we noted that infection of Purkinje cells did not result in expected transneuronal labeling of cell types that are presynaptic to Purkinje cells such as molecular layer interneurons and granule cells. However, these cell types were readily infected when RABV was injected directly in the cerebellar cortex. Conversely, neurons in the cerebellar nuclei that project to the inferior olive did not take up RABV when this was injected in the inferior olive, whereas these cells could be infected with RABV via a transneuronal route. These results suggest that viral entry from the extracellular space depends on other factors or mechanisms than those used for retrograde transneuronal transfer. We conclude that transneuronal tracing with RABV may result in unexpected results, as not all properties of RABV seem to be ubiquitously valid.

Anterograde neuronal circuit tracing using a genetically modified herpes simplex virus expressing EGFP.

Insights into the anatomical organization of complex neural circuits provide important information about function, and thus tools that facilitate neuroanatomical studies have proved invaluable in neuroscience. Advances in molecular cloning have allowed the production of novel recombinant neuroinvasive viruses for use in transynaptic neural tracing studies. However, the vast majority of these viruses have motility in the retrograde direction only, therefore limiting their use to studies of synaptic input circuitry. Here we describe the construction of an EGFP reporting herpes simplex virus, strain H129, which preferentially moves along synaptically connected neurons in the anterograde direction. In vitro and in vivo characterization studies confirm that the HSV-1 H129-EGFP retains comparable replication and neuroinvasiveness as the wildtype H129 virus. As a proof of principle we confirm anterograde movement of the H129-EGFP along polysynaptic pathways by inoculating the upper airways and tracking time-dependent EGFP expression in previously described ascending sensory pathways. These data confirm a genomic locus for recombining HSV-1 H129 such that normal viral function and replication is maintained. Novel viral recombinants such as HSV-1 H129-EGFP will be useful tools for delineating the central organization of peripheral sensory pathways as well as the synaptic outputs from central neuronal populations.

Neurological suppression of diaphragm electromyographs in hamsters infected with West Nile virus.

To address the hypothesis that respiratory distress associated with West Nile virus (WNV) is neurologically caused, electromyographs (EMGs) were measured longitudinally from the diaphragms of alert hamsters infected subcutaneously (s.c.) with WNV. The EMG activity in WNV-infected hamsters was consistently and significantly (P

Charcot's arthropathy secondary to herpetic encephalitis sequelae: an unusual presentation.

Neuropathic arthropathy (Charcot's arthropathy) is a progressive articular disease associated with a reduced sensorial and protector proprioceptive reflex. Its etiology includes many different conditions such as syringomyelia, traumatic lesion causing medullary deformity, spina bifida, diabetic neuropathy, leprosy neuropathy, neurofibromatosis, amyloid neuropathy, alcohol, and repetitive injection of hydrocortisone into joints, among others. However, the relationship between Charcot's arthropathy and herpetic encephalitis has not yet been described. Herpes encephalitis causes acute and chronic diseases of the peripheral or central nervous system. It can manifest as subacute encephalitis, recurrent meningitis, or myelitis. It can also resemble psychiatric syndromes, diplopia, sensory changes in the face and limbs, personality changes, frontal dysexecutive syndrome, stiff neck, subclinical alterations of the vestibular function, intracranial hypertension, convulsion, hemiparesis, and generally includes motor components, among others. On the other hand, pure peripheral sensory disturbance has not been described. In this article, we report the clinical case of a patient with Charcot's arthropathy secondary to pure peripheral sensory polyneuropathy as a consequence of progressive herpetic encephalitis sequelae. In this article, the authors report the first case of Charcot's arthropathy secondary to herpetic encephalitis.

Serial stellate ganglion blocks for intractable postherpetic itching in a pediatric patient: a case report.

BACKGROUND: While intractable itching may be rarely associated with postherpetic neuralgia, it can have catastrophic complications if present. METHOD: We highlight a severe case of postherpetic itching in a 10-year-old male with Fanconi's and aplastic anemia, refractory to conventional treatments and requiring intravenous sedation. RESULTS: Our use of 3 sequential stellate ganglion blocks with 5.5 mL of 0.25% bupivacaine provided significant improvement of the symptoms for 4 months after the last procedure. CONCLUSION: Although further evaluation is needed, we feel that novel use of sympathetic blockade may provide treatment for intractable itching. Highlighted is the possible influence of the sympathetic system in the pathophysiology of postherpetic itch. IMPLICATION: The use of serial stellate ganglion blocks may be a treatment option for patients with intractable itching and postherpertic neuralgia of the neck and arm region. This technique may lead to more permanent solutions such as pulse radiofrequency lesion or chemical neurolysis of sympathetic ganglions for postherpetic itch.

[Observation on the central afferent pathway of "Guanyuan" (CV 4) under normal and pathological states and the influence of electroacupuncture].

OBJECTIVE: To investigate the afferent pathways of "Guanyuan" (CV 4) under normal and pathological states and to observe the effect of electroacupuncture (EA) on them. METHODS: Twenty-four female SD rats were randomly divided into normal control (NC), NC + EA, ovariectomy (OVX) and OVX + EA groups, with 6 cases in each. Four weeks after OVX, Pseudorabies Virus (PRV, 10 microl liquid containing 10(8) plaque-forming units) was injected into CV4. Thirty minutes after PRV injection, EA (2 Hz, 2-3 mA) was applied to CV4 for 30 minutes, once daily for 3 days. Six hours after the third EA treatment, all the rats were perfused transcardially with 4% paraformaldehyde under anesthesia, followed by sampling the brain and spinal cord and cutting into sections (35 microm). Immunohistochemical method (rabbit anti-rat beta-galactosidase) was used to display PRV immunoreactive (PRV-IR) positive neurons. RESULTS: 1) After injection of PRV, PRV-IR positive cells widely distributed in the spinal cord (cervical, thoracic and lumbar segments), brain stem (nucleus of solitary tract, cuneate nucleus, gigantocellular reticular nucleus, nucleus of spinal tract of trigeminal nerve, nucleus raphe magnus, locus caeruleus, etc), hypothalamus and cerebral cortex in each group. 2) After OVX, apparently fewer PRV-IR positive cells were found in some nuclei as medial septum nucleus (MSN), arcuate nucleus (ARC), diagonal band nucleus (DBN), paraventricular nucleus (PVN) which have close relation with endocrine activity (P<0.05); and rarely seen in ventromedial hypothalamus (VMH) and lateral preoptic area (LPO) (P<0.01). But in OVX + EA group, PRV-IR positive cells in above regions or nuclei increased significantly (P<0.05 or P<0.01). No obvious difference was found between NC and NC+ EA groups in the number of PRV-IR positive cells (P>0.05). CONCLUSION: Following OVX, PRV-IR positive cells in neuroendocrine-related nuclei of hypothalamus reduced significantly in number; EA of "Guanyuan" (CV 4) can promote the recovery of these neurons in above mentioned nuclei.

Anterograde transneuronal viral tracing of central viscerosensory pathways in rats.

Previous studies demonstrated that strain H129 of herpes simplex virus-1 undergoes anterograde transneuronal transport in mice and primates after peripheral or central injection. In this study, H129 was used in rats to identify CNS regions that receive relayed viscero-sensory inputs from the stomach wall. We also examined whether transneuronal viral transport in this model is exclusively anterograde. H129 or an established retrograde transneuronal viral tracer, pseudorabies virus (PRV), was injected into the ventral stomach wall in intact rats or in rats with previous subdiaphragmatic vagal sensory deafferentation. Rats were perfused with fixative 3-5 d later, and tissues were processed for immunocytochemical detection of transported virus. In intact rats, H129 was transported transneuronally via vagal and spinal viscerosensory neurons to postsynaptic target cells in the medullary dorsal vagal complex and thoracic dorsal horn, respectively, with subsequent transport to discrete regions of the medullary and pontine reticular formation, cerebellum, parabrachial nucleus, periaqueductal gray, thalamus, hypothalamus, amygdala, bed nucleus of the stria terminalis, and other central sites. Comparison of labeling patterns in intact and vagal deafferented rats indicated that H129 also produced first-order retrograde infection of autonomic neurons that project directly to virus injection sites, similar to PRV. Unlike PRV, however, H129 was not transported transneuronally in the retrograde direction from infected neurons to central sources of presynaptic input. We conclude that transneuronal transport of H129 occurs exclusively in the anterograde direction to reveal CNS regions that receive direct and relayed viscerosensory signals.

Neural circuitry of the kidney: NO-containing neurons.

The neurons synthesizing nitric oxide (NO) that are part of the renal sympathetic pathways were located by double-staining for the neuronal isoform of nitric oxide synthase (nNOS) using immunocytochemistry to identify NO-synthesizing neurons and transneuronal tracing following infection of the left kidney with pseudorabies virus (PRV). Following kidney injection with PRV, the animals survived 4-day post-inoculation prior to sacrifice and tissue processing. PRV-infected neurons that double-stained for nNOS were found in the paraventricular hypothalamic nucleus (PVN), the raphe obscurus nucleus (ROb), the ventromedial medulla (VMM), the rostral ventrolateral medulla (rVLM) and the A5 cell group. In the thoracolumbar spinal cord, nNOS neurons co-localized with PRV-infected cells in the dorsal horn in laminae I, III-V ipsilateral to the injected kidney and in lamina X, the intermediolateral cell column, the lateral funiculus, the intercalated nucleus and the central autonomic area. We conclude that NO synthesizing cells may significantly affect renal autonomic pathways in the rat by interacting with the renal sensory and sympathomotor circuitry at multiple sites.

Corneal infection of herpes simplex virus type 2--induced neuronal apoptosis in the brain stem of mice with expression of tumor suppressor gene (p53) and transcription factors.

To understand the mechanism of neuronal apoptosis induced by herpes simplex virus (HSV) infection in vivo, the distribution of viral antigen, the appearance of apoptotic bodies, and the expressions of the tumor suppressor gene p53 and several transcription factors such as c-fos, c-jun and NF-kappaB were examined immunohistochemically and histopathologically after corneal infection of mice with HSV type 2 strain 186. Five days after HSV infection, viral antigen was diffusely detected in the corneal epithelium, the trigeminal ganglion and the pars caudalis of the spinal trigeminal nucleus. Neuronal apoptosis was observed in the brain stem ipsilateral to the HSV-infected side with the immunoreactivities of c-fos, c-jun, NF-kappaB and p53. Dual-labeling immunohistochemical studies revealed that almost all of the viral antigen-positive neurons and glia in the brain stem also showed p53 immunoreactivity. On the other hand, no neuronal apoptosis but only with the expression of c-jun was found in the trigeminal ganglion. Our results suggest that the different expression of transcription factors between the brain stem and the trigeminal ganglion may influence the neuronal apoptosis induced by HSV infection.

Anterograde tracing of trigeminal afferent pathways from the murine tooth pulp to cortex using herpes simplex virus type 1.

Due to its predominantly nociceptive innervation, viral tracing from the tooth pulp provides a potential means for tracing central pain pathways. The neural pathways from the tooth pulp to cortex were determined using in situ hybridization to detect the anterograde transneuronal spread of herpes simplex virus type 1 strain H129 following inoculation into the murine mandibular incisor pulp. Virus first appeared in the brain at day 3 in the dorsomedial region of all three subnuclei of the spinal trigeminal nucleus and the principal sensory nucleus. By days 5-6 virus had spread to the contralateral medial nucleus of the medial geniculate complex, posterior thalamus, and ventroposteromedial thalamus. At days 7-8 virus was detected in laminae IV and Va of the primary somatosensory cortex and lamina IV of the secondary somatosensory cortex in regions previously shown to receive input from the lower jaw. Several mice also showed infection of laminae II/III of the ipsilateral dysgranular insular cortex, along with labeling for virus in the ipsilateral external lateral parabrachial nucleus, posterior thalamus, and posterior basolateral amygdala. Our results are highly consistent with previous tracing and electrophysiological studies utilizing the tooth pulp and with studies implicating the infected structures in nociception. Viral spread appeared to define two separate afferent systems with infection of structures which have been implicated in the sensory-discriminative aspects of pain, such as the ventroposteromedial thalamus and somatosensory cortex, as well as in the dysgranular insular cortex and related subcortical nuclei which may have a role in the affective-motivational aspects of pain.