LCM Disease of the Adult Rat: Morphological Alterations of the Brain

Summary

LCM virus, strain WE, multiplies readily in the brain of young adult Sprague-Dawley rats with maximum titers of close to 108 ID50/g of tissue, which are reached by day 5. Five to 6 days after the intracerebral inoculation of 10⁶ mouse ID50 clinical signs develop which closely resemble the ones seen in mature mice infected via the brain. The morphological alterations, too, are similar in both species, although in the rat they are more widespread, involving parts of the brain which remain essentially normal in the mouse. In the rat, inflammatory reactions are found in the meninges, predominantly in the basal regions, as well as in circumventricular organs, such as plexus chorioidei, subfornical organ, area postrema, organum vasculosum laminae terminalis, and median eminence. In severe cases, the ventricular ependyma too is largely destroyed, and beneath the ependyma distentions of the intercellular spaces and structural changes of myelinated axons occur. Here, perivascular round cell infiltrates dominate the picture, whereas in other areas, such as the hypothalamus, the thalamus, and the cerebellar nuclei, a diffuse distribution of inflammatory elements is accompanied by a moderate glial reaction.

The observed predilection of pathological alterations in circumventricular organs suggests that peculiarities of this structurally and functionally unique system may play a relevant role in the pathogenesis of experimental LCM of the rat.