FOS protein expression and role of the vagus nerve in the rat medullary visceral zone in multiple organ dysfunction syndrome caused by subarachnoid hemorrhage

This study was designed to observe the role of FOS protein expression in the rat medullary visceral zone (MVZ) in multiple organ dysfunction syndrome (MODS) caused by subarachnoid hemorrhage (SA H), with and without severing the vagus nerve. We also investigated the regulatory and control mechanisms of the MVZ and the vagus nerve in MODS following SAH. A model of MODS following SAH was established by injecting arterial blood into the Willis' circle. The vagus nerve was cut off and blocked. The FOS protein expression in the MVZ was detected by immunohistochemistry. The positive expression levels of FOS in the MVZ in the SAH and SAH + severed-down vagus nerve (SDV) groups were higher than those in the normal control, sham surgery and SDV groups (P<0.01). However, expression in the SAH+SDV group was lower than that in the SAH group (P<0.01). Inflammatory damage was observed in each visceral organ at every time-phased point in the SAH group and the SAH+SDV group. The most apparent damage was at 24-36 h, consistent with the peak of FOS protein expression; the SAH+SDV group presented a greater level of damage. The inflammatory changes in surrounding visceral organs following SAH correlated with FOS protein expression in the MVZ, which indicates that the MVZ participates in the functional control of surrounding visceral organs following SAH. Severing the subphrenic vagus nerve increases the incidence of MODS following SA H and enhances SAH-induced inflammatory damage to the surrounding visceral organs, which indicates that the vagus nerve plays a role in the protection of the surrounding visceral organs in MODS following SAH.