Figure 2.
Neuropathology (avidin–biotin complex immunohistochemistry) and semiquantitative image densitometry of coronal brain sections of dorsal hippocampus (CA2) and external capsule of adult rats with 14-day twice daily intracerebroventricular infusions of propionic acid (PPA) or phosphate-buffered saline (PBS). Propionic acid induced significant reactive astrogliosis (anti-GFAP) and microglial activation (anti-CD68) without apoptotic neuronal cell loss (anti-cleaved caspase 3) in rat hippocampus, similar to findings in autopsied brain from patients with autism. Nuclear translocation of anti-CREB and an increase of anti-phospho-CREB immunoreactivity are observed in neural, glial, and endovascular epithelia by propionic acid treatment, suggestive of gene induction. Propionic acid increases monocarboxylate transporter 1 (MCT1) immunoreactivity, primarily in white matter external capsule, suggestive of alterations in brain short–chain fatty acid transport/metabolism. Black bars indicate propionic acid–treated animals; white bars indicate PBS (vehicle)–treated animals. Horizontal measurement bar = 100 μ. Reproduced with permission from MacFabe (2012), Microbial Ecology in Health and Disease.