ISSN:
1432-1912
Keywords:
Rabbit caudate nucleus
;
Dopaminergic neurones
;
Presynaptic receptors
;
Dopamine
;
Nomifensine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Slices of the head of the rabbit caudate nucleus were preincubated with 10−7 M 3H-dopamine and then superfused, and the effect of unlabeled dopamine on the outflow of tritium was investigated. In most experiments, nomifensine was added throughout superfusion in order to block uptake of the unlabeled amine. Nomifensine was a potent inhibitor of the uptake of 3H-dopamine into rabbit caudate synaptosomes, with an IC50 of 5·10−8 M at a 3H-dopamine concentration of 4·10−8 M. In the absence of nomifensine, unlabeled dopamine (10−7 M and higher concentrations) accelerated the basal outflow of tritium from preincubated slices. 10−5 M nomifensine strongly counteracted the acceleration. In the presence of nomifensine, unlabeled dopamine (10−7 to 10−6 M) caused a concentrationdependent decrease of the overflow of tritium evoked by electrical stimulation at 0.1 Hz. Chlorpromazine and haloperidol (in the presence of nomifensine) increased the stimulation evoked overflow and antagonized the inhibitory effect of dopamine. It is concluded that extracellular dopamine shares with other dopaminergic agonists the ability to inhibit action potential-evoked release of intraneuronal dopamine. The inhibition is mediated by specific receptors. The results support the hypothesis that previously released dopamine, by an action on these receptors, can inhibit further release of dopamine.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00515593
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