IL‐1β, TNFα and IL‐6 induction in the rat brain after partial‐body irradiation: role of vagal afferents

Abstract

Purpose: To evaluate the central nervous system neuroimmune and inflammatory responses during the prodromal phase of the acute irradiation syndrome in rat brains after partial‐body exposure (head‐protected) and to investigate the potential neural signalling pathways from the irradiated periphery to the non‐irradiated brain.

Material and methods: The study included four groups of rats: one irradiated group and one sham irradiated group, each containing non‐vagotomized and vagotomized rats. In vagotomized rat groups, the subdiaphragmatic vagal section surgery was carried out 45 days before the irradiation exposure. The rats were partial‐body irradiated with the head shielded with ⁶⁰Co γ‐rays to a dose of 15 Gy. They were sacrificed 6 h after the end of exposure. The hypothalamus, hippocampus, thalamus and cortex were then collected, and the concentrations of IL‐1β, TNFα and IL‐6 in each were measured by ELISA assays.

Results: Six hours after irradiation, IL‐1β levels had increased in the hypothalamus, thalamus and hippocampus, and TNFα and IL‐6 levels had increased significantly in the hypothalamus. Vagotomy before irradiation prevented these responses.

Conclusions: It was concluded that the hypothalamus, hippocampus, thalamus and cortex react rapidly to peripheral irradiation by releasing pro‐inflammatory mediators. The results also show that the vagus nerve is one of the major ascending pathways for rapid signalling to the brain with respect to partial body irradiation.