After the injection of Herpes Simplex Virus type 1 into the rat cervic
al vagus nerve, transneuronally labelled virus-containing neurons and
glial cells were present in the medulla oblongata. Fos-containing nucl
ei were present in the same regions of the brain. A double-labelling p
rocedure revealed that most of the virus-positive neurons also contain
ed Fos-positive nuclei. Appearance of HSV1 antigen within the CNS is a
ssociated with Fos expression in neurons and glial cells.