Autoregulation of Catecholamine Release at Central and Sympathetic Nerve Terminals: Common Features

ABSTRACT Autoregulation of catecholamine release was investigated both in vivo at central nerve endings and in vitro at sympathetic fibers by means of carbon fiber electrodes combined with electrochemical detection. Release was evoked by electrical stimulation at physiological frequencies. The evoked dopamine and noradrenaline release are attenuated respectively by D 2 and alpha-2 agonists and enhanced by antagonists. Autoreceptors are located either on terminals or on glial cells embedding them. In physiological conditions, the extracellular catecholamine level is the chemical signal which drives autoinhibition. Autoregulation prevents excessive release which could be triggered by prolonged bursts of action potentials.