The content and turnover of norepinephrine was measured in the interscapular brown adipose tissue (BAT), white adipose tissue (WAT) and heart of lean and monosodium glutamate treated obese rats (GOR). An HPLC-ECD method was used for efficient separation and sensitive detection of catecholamines with an appropriate sample preparation, especially for lipid rich tissues. The lower basal norepinephrine level and the slower norepinephrine turnover in organs of the glutamate obese rats indicate a diminished activity of the sympathetic nervous system which may be a reason for a reduced thermogenic response and in this way contributes to the development of obesity.