Evidence for a similar compartmentation of recaptured and endogenously synthesized dopamine in striatal synaptosomes |
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Authors: | Franca Cerrito Gianna Casazza Giulio Levi Maurizio Raiteri |
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Institution: | (1) Instituto di Farmacologia, Università Cattolica, Via Pineta Sacchetti 644, 00168 Rome;(2) Laboratorio di Biologia Cellulae, CNR, Via Romagnosi 18A, Rome, Italy |
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Abstract: | The aim of the present study was to compare the release pattern of 3H]dopamine (3H]DA) originated from 3H]tyrosine or by uptake in striatal synaptosomes. Synaptosomes prelabeled either with 3H]DA or with 3H]tyrosine were superfused in three conditions stimulating DA release by different mechanisms: (1) depolarization with high K+; (2) inversion of the Na+ gradient across the plasma membrane; (3) exposure tod-amphetamine. Since DA contained in different pools may exit from nerve endings by different processes, DA release was analyzed in the presence or in the absence of nomifensine which allows discrimination between carrier-mediated and carrier-independent processes. The pattern of DA release in the three conditions tested was identical, whether 3H]DA originated from synthesis or from uptake. Nomifensine did not affect the high-K+-induced release and inhibited that induced by the other two stimuli. The results suggest that newly synthesized and recaptured DA have a similar compartmentation in nerve endings. |
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