Measurement of endogenous dopamine and norepinephrine release from superfused slices of rat prefrontal cortex in vitro: modulation by D2 and alpha-2 presynaptic receptors.

Endogenous dopamine (DA) and norepinephrine (NE) in the superfusate from slices of rat medial prefrontal cortex were measured by high-performance liquid chromatography coupled to electrochemical detection (HPLC-ECD). Stimulation with high K+ or methamphetamine (MAP) evoked a dose-dependent elevation in the release of DA and NE, although spontaneous release of DA or NE was barely detectable. The K(+)-evoked release was Ca++ dependent, whereas the MAP-evoked release was not. The K(+)-evoked DA release was inhibited by the DA agonist apomorphine (1 microM or 10 microM) and enhanced by the D2 antagonist (-)-sulpiride (1 microM). The K(+)-evoked NE release was inhibited by the alpha-2 agonist clonidine (0.1 microM or 1 microM) and enhanced by the alpha-2 antagonist idazoxan (1 microM). These results confirm the existence of release modulatory D2 and alpha-2 receptors in the medial prefrontal cortex. The present study is the first description of a method which allows evaluation of the release of endogenous DA or NE in the cortex slices and is competent to examine the properties of the two catecholamines release and their regulation by presynaptic receptors.