ß3-adrenoreceptor agonists can stimulate lipolysis in the white adipose tissue and thermogenesis in the brown adipose tissue. These activities could be useful in the treatment of obesity and the associated metabolic syndrome. The effects of six-week oral administration of the newly synthesized substance B496 (methyl-4-[2- -[2-hydroxy-3-(4-ethylcarbamoyl)phenoxyprophyl]amino]etyl)-phenoxyacetate hydrochloride) on serum glucose, triglycerides, total cholesterol, and leptin levels were studied in male Wistar rats fed with a high-fat diet. The animals were divided into a group treated with B496 (5 mg dissolved in 1 litre of water) and a control group. The results indicated a significant reduction in serum glucose levels (-26 %, p<0,01), triacylglyceride levels (-21 %, p<0,05) and leptin levels (-43 %, p<0,01). Further the effect of a single intraperitoneal dose (1 mg/kg) of B496 and BRL-37344 on serum leptin levels in the C57Bl/6J mouse was investigated. Administration of BRL-37344 resulted in a significant decrease in serum leptin levels (-55 %, p<0,001). This reduction was not demonstrated by newly synthesized substance B496.

        Key words: ß3-adrenoreceptor agonist – aryloxypropanolamines – leptin – BRL-37344