Tumor necrosis factor-alpha in the dorsal vagal complex suppresses gastric motility

Gastric hypomotility, loss of appetite, nausea, and vomiting frequently accompany critical infectious illness, radiation sickness, and carcinogenesis. The present studies examined the possibility that the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), may be responsible for provoking some of these autonomic signs associated with illness. Gastric motility of urethane-anesthetized rats was prestimulated with intracisternal applications of thyrotropin-releasing hormone (TRH), a peptide known to activate parasympathetic vagal excitatory pathways to the stomach. Microinjection of TNF-alpha (as low as 0.02 fmol) directly into the dorsal vagal comples (DVC) suppressed TRH-stimulated gastric motility for prolonged periods of time. Duration of suppression ranged from 5 min to more than an hour, dependent on both the dose of TNF-alpha and accuracy of placement of the microinjection within the DVC. This suppression demonstrated a dose-dependent effect of TNF-alpha that required an intact vagal pathway. These studies indicate that TNF-alpha may represent a unique cytokine 'afferent' signal which directly regulates the excitability of vago-vagal reflex circuits resulting in altered gastric motility during disease states.