Perinatal exposure to infectious agents and toxins is linked to the pathoge
nesis of neuropsychiatric disorders, but the mechanisms by which environmen
tal triggers interact with developing immune and neural elements to create
neurodevelopmental disturbances are poorly understood. We describe a model
for investigating disorders of central nervous system development based on
neonatal rat infection with Borna disease virus, a neurotropic noncytolytic
RNA virus. Infection results in abnormal righting reflexes, hyperactivity.
inhibition of open-field exploration, and stereotypic behaviors. Architect
ure is markedly disrupted in hippocampus and cerebellum, with reduction in
granule and Purkinje cell numbers. Neurons are lost predominantly by apopto
sis, as supported by increased mRNA levels for pro-apoptotic products (Fas,
caspase-1), decreased mRNA levels for the anti-apoptotic bcl-x, and in sit
u labeling of fragmented DNA. Although inflammatory infiltrates are observe
d transiently in frontal cortex, glial activation (microgliosis z astrocyto
sis) is prominent throughout the brain and persists for several weeks in co
ncert with increased levels of proinflammatory cytokine mRNAs (interleukins
1 alpha, 1 beta, and 6 and tumor necrosis factor alpha) and progressive hi
ppocampal and cerebellar damage. The resemblance of these functional and ne
uropathologic abnormalities to human neurodevelopmental disorders suggests
the utility of this model for defining cellular, biochemical, histologic, a
nd functional outcomes of interactions of environmental influences with the
developing central nervous system.