Summary
In vasa deferentia of reserpine-pretreated rats a carrier-mediated (i. e., desipramine-sensitive) outward trAnsport of endogenous dopamine was induced by either tyramine or ouabain. The dopamine taking part in the efflux induced by tyramine (and the concomitant efflux of DOPAC) was derived from ongoing synthesis of dopamine.
Inhibition of MAO trebled the rate of spontaneous efflux of dopamine and reduced the spontaneous efflux of DOPAC by 90%. After inhibition of MAO, desipramine caused a further five-fold increase in the basal efflux of dopamine with no change in the basal efflux of DOPAC. Inhibition of COMT failed to affect the spontaneous efflux of dopamine but increased that of DOPAC.
It is concluded that, after depletion of the noradrenaline stores by pretreatment with reserpine, an outward transport of axoplasmic dopamine is induced by the same mechanisms that (without any pretreatment with reserpine) are known to initiate an outward transport of noradrenaline.
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Abbreviations
- COMT:
-
catechol-O-methyl transferase
- DOPAC:
-
dihydroxyphenylacetic acid; HVA homovanillic acid
- MAO:
-
monoamine oxidase
References
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Supported by the Dr. Robert Pfleger-Stiftung and the Deutsche Forschungsgemeinschaft (SFB 176 and Gr 490/5)
Supported by the Alexander von Humboldt-Stiftung
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Langeloh, A., Halbrügge, T. & Trendelenburg, U. Carrier-mediated outward transport of dopamine from adrenergic varicosities of the vas deferens of reserpine-pretreated rats. Naunyn-Schmiedeberg's Arch Pharmacol 344, 619–622 (1991). https://doi.org/10.1007/BF00174744
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DOI: https://doi.org/10.1007/BF00174744