Neuronal premotor networks involved in eyelid responses: retrograde transneuronal tracing with rabies virus from the orbicularis oculi muscle in the rat.

Retrograde transneuronal tracing with rabies virus from the right orbicularis oculi muscle was used to identify neural networks underlying spontaneous, reflex, and learned blinks. The kinetics of viral transfer was studied at sequential 12 hr intervals between 3 and 5 d after inoculation. Rabies virus immunolabeling was combined with the immunohistochemical detection of choline acetyltransferase expression in brainstem motoneurons or Fluoro-Ruby injections in the rubrospinal tract. Virus uptake involved exclusively orbicularis oculi motoneurons in the dorsolateral division of the facial nucleus. At 3-3.5 d, transneuronal transfer involved premotor interneurons of trigeminal, auditory, and vestibular reflex pathways (in medullary and pontine reticular formation, trigeminal nuclei, periolivary and ventral cochlear nuclei, and medial vestibular nuclei), motor pathways (dorsolateral quadrant of contralateral red nucleus and pararubral area), deep cerebellar nuclei (lateral portion of interpositus nucleus and dorsolateral hump ipsilaterally), limbic relays (parabrachial and Kölliker-Fuse nuclei), and oculomotor structures involved in eye-eyelid coordination (oculomotor nucleus, supraoculomotor area, and interstitial nucleus of Cajal). At 4 d, higher order neurons were revealed in trigeminal, auditory, vestibular, and deep cerebellar nuclei (medial, interpositus, and lateral), oculomotor and visual-related structures (Darkschewitsch, nucleus of the posterior commissure, deep layers of superior colliculus, and pretectal area), lateral hypothalamus, and cerebral cortex (particularly in parietal areas). At 4.5 and 5 d the labeling of higher order neurons occurred in hypothalamus, cerebral cortex, and blink-related areas of cerebellar cortex. These results provide a comprehensive picture of the premotor networks mediating reflex, voluntary, and limbic-related eyelid responses and highlight potential sites of motor learning in eyelid classical conditioning.

Neuroimmunopathogenesis of ts1 MoMuLV viral infection.

Newborn mice infected with ts1, a mutant of the Moloney murine leukemia virus, develop neuroimmunodegeneration with death and damage of thymocytes, astrocytes, and motor neurons by 24-38 days. T cells, B cells, and astrocytes, but not neurons, are infected by the virus. Primary splenocytes and thymocytes isolated from age-matched infected or control mice, when incubated in serum-deficient media containing phytohemagglutinin-L, either homotypically aggregate and survive or swell, expose their inner membrane phospholipids, and then shrink as they fragment their nuclei and excrete DNA-containing hypoploid minicells. In our present studies, the rates of these apoptotic changes were greatly increased in the infected cells. This thymocyte death was ameliorated in vitro by addition of Th2 cytokines, but not by Th1 cytokines, or by redox agents. In contrast, death of splenocytes, which were already mitogenically activated in vivo by the virus, was prevented by Th1 and Th2 cytokines plus redox support. In vivo, this ts1-induced neuroimmunodegenerative syndrome could be completely prevented by the immunomodulator polyinosine-cytosine and partially prevented by cytokines or redox modifiers. Viral titer primarily in the brain was also diminished by polyinosine-cytosine therapy. These observations indicate that the cell death in T cells and neurons in these ts1-infected neonatal mice can be prevented in vitro and in vivo by appropriate upregulation of the immune system.