PHARMACOLOGICAL CHARACTERIZATION OF DOPAMINE AUTORECEPTORS IN THE RAT VENTRAL TEGMENTAL AREA - MICROIONTOPHORETIC STUDIES

  • 1 January 1984
    • journal article
    • research article
    • Vol. 231  (2) , 275-280
Abstract
Extracellular single-cell recording and microiontophoretic techniques were used to characterize the presynaptic dopamine (DA) receptors (autoreceptors) on A10 DA neurons in the rat ventral tegmental area. The ability of various agonist to inhibit the activity of A10 DA neurons was compared. DA and the DA agonist N-n-propylnorapomorphine (NPA), apomorphine, lisuride, pergolide, LY141865 and bromocriptine all suppressed the activity of A10 DA neurons. NPA was the most potent exogenous agaonist, exerting effects that were similar to an equimolar concentration of DA (0.01 M). When ejected at equimolar concentrations (0.01 M) and equivalent ejection currents, the rank order of potency for these agonists was DA = NPA > LY141865 > pergolide = lisuride = apomorphine > norepinephrine > bromocripitine. The .alpha.-2 adrenoceptor agonist clonidine, the .beta. adrenoceptor agonist isoproterenol, the D-1 specific DA agonist SKF 38393 and the hallucinogenic ergot LSD exerted only weak effects or were inactive. The D-2 specific DA antagonist sulpiride completely blocked the rate-suppressant effects of DA and DA agonists but not those of .gamma.-aminobutyric acid. The purported D-1 specific DA antagonist SCH 23390 failed to block the effects of either DA or the D-2 specific DA agaonist LY141865. Results indicate that DA agonists suppress the activity of the majority of A10 DA neurons by acting directly on somatodendritic DA autoreceptors which exhibit the pharmacological characteristics of D-2 receptors.