The blood-brain barrier (BBB) is no longer considered a static wall restricting circulating peptides from the brain. Many peptides have been shown to penetrate the BBB, some by diffusion and some by selective transport mechanisms. The interaction of alcohol at the BBB with certain peptides that can affect alcohol ingestion would provide a novel site of regulation. It is proposed that alcohol increases the entry of angiotensin II (AT), cholecystokinin-8 (CCK), leptin, and tumor necrosis factor-alpha (TNF) into brain from the circulation, thus inhibiting alcohol ingestion. The effects of alcohol ingestion on the rate and saturation (self-inhibition) of entry of peripherally injected AT, CCK, leptin, and TNF into the brains of mice will be determined by multiple-time regression analysis and also blood-free perfusion. HPLC will determine that the iv injected substance reaches the brain intact, capillary depletion with washout will show that it is not bound to the capillary endothelium or loosely associated with vascular elements, and measurement of efflux from brain will rule out possible confounding effects on influx. Simultaneous injection of albumin will control for leakage of blood and non-specific entry. Cross-inhibition, particularly of TNF on leptin transport, will determine whether TNF affects leptin at the BBB as it does at the adipocyte. Alcohol-induced transport of these four substances into brain is probably at least partially mediated by transporters different from their receptors. After the isolation and identification of these transport proteins, the effects of ethanol on their distribution in brain will be quantified by autoradiographic image analysis. These sensitive procedures will show that the BBB serves as a dynamic site for the interaction of alcohol and peptides.
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