Electrical stimulation of afferent vagus nerve induces IL-1 beta expression in the brain and activates HPA axis

Possible roles of the afferent vagus nerve in regulation of interleukin (IL )-1 beta expression in the brain and hypothalamic-pituitary-adrenal (HPA) a xis were examined in anesthetized rats. Levels of IL-1 beta mRNA and protei n in the brain were measured by comparative RT-PCR and ELISA. Direct electr ical stimulation of the central end of the vagus nerve was performed contin uously for 2 h. The afferent stimulation of the vagus nerve induced increas es in the expression of mRNA and protein levels of IL-1 beta in the hypotha lamus and the hippocampus. Furthermore, expression of corticotropin-releasi ng factor mRNA was increased in the hypothalamus 2 h after vagal stimulatio n. Plasma levels of ACTH and corticosterone were also increased by this sti mulation. The present results indicate that activation of the afferent vagu s nerves itself can induce production of IL-1 beta in the brain and activat e the HPA axis. Therefore, the afferent vagus nerve may play an important r ole in transmitting peripheral signals to the brain in the infection and in flammation.