Presynaptic Adenosine A2 and N-Methyl-D-Aspartate Receptors Regulate Dopamine Synthesis in Rat Striatal Synaptosomes |
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Authors: | Muhammad Chowdhury Marianne Fillenz |
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Institution: | University Laboratory of Physiology, Oxford, England. |
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Abstract: | Dopamine synthesis rate and cyclic AMP concentration were measured in synaptosomes prepared from rat striatum. Dopamine synthesis rate was decreased by the addition of either adenosine deaminase or 8-phenyltheophylline, an adenosine receptor blocker, and was increased by the addition of 2-chloroadenosine. The addition of L-glutamate in the absence of adenosine deaminase decreased both dopamine synthesis rate and cyclic AMP concentration; in the presence of adenosine deaminase, glutamate had no effect on basal dopamine synthesis, but enhanced K(+)-stimulated synthesis. Both these effects of glutamate were abolished in Ca2(+)-free medium or in the presence of 2-amino-5-phosphonovalerate, an N-methyl-D-aspartate (NMDA) receptor blocker. In Mg2(+)-free medium with adenosine deaminase, glutamate enhanced both basal and K(+)-stimulated synthesis. These results suggest that dopaminergic terminals have A2 adenosine receptors, whose activation can stimulate dopamine synthesis by a cyclic AMP-dependent mechanism, and NMDA receptors, which modulate dopamine synthesis by a Ca2(+)-dependent mechanism. |
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Keywords: | Presynaptic N-methyl-D-aspartate receptors A2 receptors Striatal dopamine synthesis |
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