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Two experiments examined the contribution of the two catecholamines--epinephrine (EPI) and norepinephrine (NE)--to the control of food intake and body weight gain in male rats during chronic exercise. Urinary excretion of both catecholamines rose significantly and was positively correlated to food intake inhibition (NE, n = 54, r = 0.394, p less than 0.01; EPI, n = 54, r = 0.428, p less than 0.01). Oral ingestion of the non-selective beta-adrenoceptor blocking drug, pindolol, abolished the food intake reduction induced by exercise. Furthermore, rats that were treated with pindolol gained weight at a higher rate than untreated rats. These findings are consistent with the idea that catecholamines contribute to post-exercise inhibition of food intake and reduction of body weight in male rats. However, the exact physiological mechanism of catecholamine-induced decrease in food intake remains to be elucidated.

Plasma dopamine-beta-hydroxylase activity and catecholamines (adrenaline and noradrenaline) level in venous blood taken from the cubital vein and in arterialized capillary blood taken from the ear lobe were measured before and after a maximal exercise on a treadmill in 14 healthy untrained volunteers. The authors have shown a good correlation between these parameters in venous blood and those in capillary blood. It is concluded that the determination of plasma dopamine-beta-hydroxylase activity and catecholamines level in arterialized capillary blood could be a valid measure of the sympathetic activity.

The use of sensitive detectors has enabled the development of high performance liquid chromatography (HPLC) for the dosage of plasma catecholamines (adrenalin, A; noradrenalin, NA and dopamine, DA). Separation of the catecholamines may be done with a pair of ions chromatography on grafted silica or with an exchange of ions chromatography. The quantification is carried out, either by electro-chemical detection (HPLC-ECD), or by fluorometry after catecholamines shunting into trihydroxyindoles compounds (THI). The THI method, more sensitive, does not permit the detection of DA. Plasma levels of A or NA of 30 pg/ml (or 150 fmol/ml) may be measured by HPLC-ECD). The validation of this method as compared with a radioenzymatic method (RA-COMT) permits to imagine that the HPLC-ECD method, which has the advantage of being more economical, less complex and faster than the RA-COMT method, represent a useful tool for the exploration of the adrenergic system clinically as well as in research.