Norepinephrine release in the rat frontal cortex under treadmill exercise: a study with microdialysis.

Cortical norepinephrine (NE) release and metabolism were studied by using chronic microdialysis in rats performing a treadmill exercise at 25 m/min with a 3% slope. Cortical microdialysates and peripheral blood were collected at rest, during 1- or 2-h treadmill running, and for 1 h after exercise. Microdialysate NE and its main metabolites, 3,4-dihydroxyphenylglycol and 3-methoxy-4-hydroxyphenylglycol, and plasma epinephrine (Epi) and NE were determined by high-performance liquid chromatography with electrochemical detection. The results show that treadmill running is able to stimulate concomitantly peripheral catecholamine secretion and central noradrenergic activity, i.e., NE turnover and release. The duration of the central activation and its prolongation over recovery period increases as the duration of the running increases. A positive correlation was found between the central noradrenergic activation and peripheral Epi secretion but not peripheral NE. These findings confirm and extend our previous observations in exercising men and give support to the hypothesis that the elevation of circulating Epi can be a relevant factor mediating, directly or indirectly, the exercise-induced central neurochemical, psychological, and cognitive changes.