Brainstem substrates of sympatho-motor circuitry identified using trans-synaptic tracing with pseudorabies virus recombinants.

Previous physiological investigations have suggested the existence of a neural circuit that coordinates activation of motor and autonomic efferents before or at the onset of exercise. Traditionally these circuits have been postulated to involve forebrain areas. However, overlapping populations of medullary reticular formation neurons that participate in motor or autonomic control have been described previously, suggesting that individual pontomedullary reticular formation neurons may coordinate both motor and autonomic responses. We tested this hypothesis by conducting transneuronal retrograde tracing of motor and sympathetic nervous system pathways in rats using recombinant strains of pseudorabies virus (PRV). A PRV strain expressing the green fluorescent protein (PRV-152) was injected into the left gastrocnemius muscle, which was surgically sympathectomized, whereas another recombinant (PRV-BaBlu) was injected into the left adrenal gland. Immunofluorescence methods using monospecific antisera and distinct fluorophores identified neurons infected with one or both of the recombinants. Brainstem neurons coinfected with both PRV recombinants, which presumably had collateralized projections to both adrenal sympathetic preganglionic neurons and gastrocnemius motoneurons, were observed in several areas of the pontomedullary reticular formation. The largest number of such neurons was located in the rostral ventromedial medulla within the ventral gigantocellular nucleus, gigantocellular nucleus pars alpha, raphe obscurus, and raphe magnus. These neurons are candidates for relaying central command signals to the spinal cord.

Pathogenesis of herpes simplex virus type 2 experimental genital infection in pregnant mice.

The progression of herpes simplex-2 genital infection in pregnant mice was studied by detection of viral antigens using immunoperoxidase in tissue sections, electron microscopy and virus isolation. The majority of mice (66.66%) died at 8-9 days post-inoculation. Abortions were observed in 69.23% of the infected mice along with impairment of labor and delivery. Herpes antigens were detected in most of the autonomic nerves of the uterus, including those surrounding small arterioles in the myometrium and the Auerbach and Meissner plexa of the large bowel, but not in the abortions or placentas. The infection of uterine autonomic fibers and myometrial cells could explain the delivery impairment and could have provoked a decrease in blood flow leading to abortions.

Neuronal pathways for the propagation of herpes simplex virus type 1 from one retina to the other in a murine model.

Herpetic retinitis in humans is characterized by a high frequency of bilateral localization. In order to determine the possible mechanisms leading to bilateral retinitis, we studied the pathways by which herpes simplex virus type 1 (HSV-1) is propagated from one retina to the other after intravitreal injection in mice. HSV-1 strain SC16 (90 p.f.u.) was injected into the vitreous body of the left eye of BALB/c mice. Animals were sacrificed 1, 2, 3, 4 and 5 days post-inoculation (p.i.). Histological sections were studied by immunochemical staining. Primary retinitis in the inoculated eye (beginning 1 day p.i.) was followed by contralateral retinitis (in the uninoculated eye) starting at 3 days p.i. Infected neurons of central visual pathway nuclei (lateral geniculate nuclei, suprachiasmatic nuclei and pretectal areas) were detected at 4 days p.i. Iris and ciliary body infection was minimal early on, but became extensive thereafter and was accompanied by the infection of connected sympathetic and parasympathetic pathways. The pattern of virus propagation over time suggests that the onset of contralateral retinitis was mediated by local (non-synaptic) transfer in the optic chiasm from infected to uninfected axons of the optic nerves. Later, retinopetal transneuronal propagation of the virus from visual pathways may have contributed to increase the severity of contralateral retinitis.

Pseudorabies virus mutants as transneuronal markers.

The transneuronal labeling properties of three genetically engineered forms of the Bartha strain of pseudorabies virus (PRV) were studied in the ocular sympathetic pathway of rats. Bartha PRV mutants in which expression of the viral glycoprotein gI (homologous to gE of herpes simplex virus type 1, HSV-1) was restored (Bartha gI+) or which express a wildtype form of glycoprotein gIII (homologous to gC of HSV-1 and referred here as Bartha gIIIKa) were analyzed. In addition, a Bartha PRV mutant (Bartha beta-gal) containing the lacZ gene encoding E. coli beta-galactosidase inserted into the gX gene (homologous to gG of HSV-1) was also studied. These were compared to the parental strain--Bartha PRV. The pattern of transneuronal labeling in the intermediolateral cell column was studied 4 days after 5 microliters of different concentrations of viral stocks were injected into the anterior chamber of the eye. The optimal infectious dose required to produce the maximal number of cases with specific transneuronal labeling of sympathetic preganglionic neurons was determined and these were as follows: Bartha PRV = 10(7.5) pfu/ml, Bartha beta-galactosidase = 10(6.5) pfu/ml, Bartha gIIIKa = 10(5) pfu/ml, Bartha gI+ = 10(4) pfu/ml. An inverse relationship between specificity and infectivity rate was observed. Bartha beta-gal produced the greatest number of cases with specific labeling (76%); Bartha gI+ produced the lowest level (10%) and thus, this virus is not useful for transneuronal labeling studies. Bartha gIIIKa labeled more sympathetic preganglionic neurons (second-order neurons) than Bartha beta-gal or Bartha PRV. Bartha gIIIKa and Bartha beta-gal viruses labeled more interneurons (third-order) than the standard Bartha PRV.(ABSTRACT TRUNCATED AT 250 WORDS)