Autoregulation of Evoked Noradrenaline Release at the Surface of the Isolated Rat Tail Artery Studied by Electrochemistry

Noradrenaline release from sympathetic fibers was evoked by electrical stimulation and was monitored at the arterial surface by a carbon fiber electrode combined with differential pulse amperometry. The evoked increase in local noradrenaline concentration was reduced by the alpha-2 agonists clonidine and xylazine and doubled by the alpha-2 antagonists yohimbine and idazoxan. The attenuation induced by clonidine was more pronounced at low frequencies (1 or 2 Hz) than at higher ones (5 or 10 Hz).