Abstract
After oral challenge of the pathological prion protein, the causative agent of bovine spongiform encephalopathy, the pathogen was first detected in the distal ileum and then deposited in the brain. The present study aims determining the possible neuronal transporting pathways from the ileum to the brain in the cattle using a tracer protein. After horseradish peroxidase was injected into the wall of the distal ileum in the calf, almost all labeled neurons were detected in the celiac and cranial mesenteric ganglion complex. Only a few labeled neurons existed in the caudal mesenteric ganglion and the paravertebral ganglia. They were sympathetic postganglionic neurons. In the dorsal root ganglia T5 to L4, some sensory neurons were found to be labeled. Only a small number of parasympathetic preganglionic neurons were labeled in the dorsal motor nucleus of the vagus nerve. No labeled sensory neurons were found in the nodose ganglion. These results suggest that the pathological prion protein is mainly transported to the spinal cord and brain via the sympathetic nervous system and partially via the sensory neurons in the dorsal root ganglia. The vagus nerve does not seem to contribute to the transport of the pathogen from the ileum directly.
