The time-course of hindbrain neuronal activity varies according to location during either intraperitoneal or subcutaneous tumor growth in rats: Single Fos and dual Fos/dopamine β-hydroxylase immunohistochemistry

• Brainstem structures respond differently to i.p. and s.c. induced fibrosarcoma.
• Responses of brainstem structures depend on the stage of fibrosarcoma growth.
• Changes induced by i.p. fibrosarcoma are most prominent in VLM and AP.
• I.p. fibrosarcoma induces increase of TNF-α and IL-1β plasma levels.

Neuronal activity in the nucleus of the solitary tract, ventrolateral medulla, area postrema, and parabrachial nucleus was studied in rats with intraperitoneal or subcutaneous tumors on the 7th, 14th, 21st, and 28th day after injection of fibrosarcoma tumor cells. We found that the number of Fos and dopamine β-hydroxylase immunopositive neurons differs between animals with intraperitoneal and subcutaneous tumors and also between tumor-bearing rats at different times following injection. Our data indicate that responses of the brainstem structures to peripheral tumor growth depend on the localization as well as the stage of the tumor growth.