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.