LPS-induced suppression of gastric motility relieved by TNFR:Fc construct in dorsal vagal complex

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Abstract
Our previous studies suggested that the cytokine tumor necrosis factor-α (TNF-α) may act within the neural circuitry of the medullary dorsal vagal complex (DVC) to affect changes in gastric function, such as gastric stasis, loss of appetite, nausea, and vomiting. The definitive demonstration that endogenously generated TNF-α is capable of affecting gastric function via the DVC circuitry has been impeded by the lack of an antagonist for TNF-α. The present studies used localized central nervous system applications of the TNF-adsorbant construct (TNFR:Fc; TNF-receptor linked to the Fc portion of the human immunoglobulin IgG1) to attempt to neutralize the suppressive effects of endogenously produced TNF-α. Gastric motility of thiobutabarbital-anesthetized rats was monitored after systemic administration of lipopolysaccharide (LPS) to induce TNF-α production. Continuous perfusion of the floor of the fourth ventricle with TNFR:Fc reversed the potent gastroinhibition induced by LPS, i.e., central thyrotropin-releasing hormone-induced increases in motility were not inhibited. This disinhibition of gastric stasis was not seen after intravenous administration of similar doses of TNFR:Fc nor ventricular application of the Fc fragment of human immunoglobulin. These results validate our previous studies that suggest that circulating TNF-α may act directly within the DVC to affect gastric function in a variety of pathophysiological states.