Continuous ambulatory peritoneal dialysis (CAPD) is often associated with malnutrition; reduced intake of nutrients due to anorexia is an important factor. The glucose load from glucose-based peritoneal dialysis (PD) solutions and amino acids from amino acid-based solutions may favor suppression of the appetite. To study this matter we used a new experimental model in free-moving, unstressed male Wistar rats (300 to 350 g) with feeding catheters channeled from the top of the skull to the oral cavity. When the rats recovered from surgery they were tested under standardized conditions by giving them an intraoral infusion (1 ml/min) of a solution containing 342 g/liter of the sucrose or 97 g/liter protein solutions while recording the time (volume) of ingestion. Control rats consumed 18.8 +/- 0.9 ml of the sucrose and 39.8 +/- 0.8 ml of the protein solutions. Injections of PD solutions with 13.6, 22.7, and 38.6 g/liter of glucose reduced the ingestion of sucrose by 12.4%, 23.6% and 36.1%, respectively, but did not affect the ingestion of protein. Injections of 30 ml of PD solutions containing 11, 18 and 31 g/liter of amino acids reduced the ingestion of both sucrose by 9.7%, 17.1% and 33.2% and of protein by 13.5%, 25.9% and 33.1%, respectively. We conclude that in our experimental model, the inhibition of appetite caused by peritoneal solutions containing glucose or amino acids seems to be specific for each nutritional constituent and not simply an effect of hyperosmolality or large filling volumes.