c-Fos generation in the dorsal vagal complex after systemic endotoxin is not dependent on the vagus nerve

The present study used activation of the c-Fos oncogene protein within neur ons in the dorsal vagal complex (DVC) as a marker of neuronal excitation in response to systemic endotoxin challenge [i.e., lipopolysaccharide (LPS)]. Specifically, we investigated whether vagal connections with the brain ste m are necessary for LPS cytokine-induced activation of DVC neurons. Systemi c exposure to LPS elicited a significant activation of c-Fos in neurons in the nucleus of the solitary tract (NST) and area postrema of all thiobutaba rbital-anesthetized rats examined, regardless of the integrity of their vag al nerves. That is, rats with both vagi cervically transected were still ab le to respond with c-Fos activation of neurons in the DVC. Unilateral cervi cal vagotomy produced a consistent but small reduction in c-Fos activation in the ipsilateral NST of all animals within this experimental group. Given that afferent input to the NST is exclusively excitatory, it is not surpri sing that unilateral elimination of all vagal afferents would diminish NST responsiveness (on the vagotomized side). These data lead us to conclude th at the NST itself is a primary central nervous system detector of cytokines .