Induction of c-fos-like protein in the spinoparabrachial tract-neurons locating within the sacral parasympathetic nucleus in the rat.

Immunoreactivity against c-fos-like protein (FOS) was induced in many neuronal cell bodies within the sacral parasympathetic nucleus (SPN) in urethane-anesthetized rats by chemical irritation of the urinary bladder with formalin. More than half of these FOS-immunoreactive neurons were retrogradely labeled with Fluoro-Gold injected into the lateral parabrachial nucleus (PBN1). The results indicate that some neurons within the SPN may transmit noxious information from the urinary bladder to the PBN1.