Noradrenaline clearance differs in the frontal cortex and hypothalamus: a dual-probe microdialysis study in...

The noradrenergic innervation of the frontal cortex and the hypothalamus arises from different brainstem nuclei and neurones projecting to these two brain regions differ topographically and morphologically. In the present study, we investigated whether there is a difference in noradrenaline clearance in these two brain areas using dual-probe microdialysis in freely-moving rats. Noradrenaline clearance was determined simultaneously in each brain area by measuring the noradrenaline extraction fraction using the 'No Net Flux' method, with both brain regions perfused with the same solutions. The noradrenaline extraction fraction was greater in the frontal cortex than in the hypothalamus (72 and 54%, respectively). This finding suggests that the processes involved in noradrenaline clearance, especially uptake, are more efficient in the former brain area, which could explain the differences in the increase in noradrenaline efflux when these brain areas are challenged with drugs that alter the function of the central nervous system.