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| Dopamine selects glutamatergic inputs to neostriatal neurons |
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FloresHernandez, J; Elvira Galarraga; José Bargas Diaz; |
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Publication date:
1997 |
| Journal:
SYNAPSE |
| Volume:
25 |
| Issue:
2 |
| Pages:
185-195 |
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| Glutamatergic synaptic potentials induced by micromolar concentrations of the potassium conductance blocker 4-aminopyridine (4-AP) were recorded intracellularly from rat neostriatal neurons in the presence of 10 mu M bicuculline (BIC). These synaptic potentials originate from neostriatal cortical and thalamic afferents and were completely blocked by 10 mu M 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) plus 100 mu M D-2-amino-5-phosphonovaleric acid (8-APV). Their inter-event time intervals could be fitted to exponential distributions, suggesting that they are induced randomly. Their amplitude distributions had most counts around 1 mV and fewer counts with values up to 5 mV. Since input resistance of the recorded neurons is about 40 MR, the amplitudes agree to quantal size measurements in mammalian central neurons. The action of a D-2 agonist, quinpirole, was studied on the frequency of these events. Mean amplitude of synaptic potentials was preserved in the presence of 2-10 mu M quinpirole, but the frequency of 4-AP-induced glutamatergic synaptic potentials was reduced in 35% of cases. The effect was blocked by the D-2 antagonist sulpiride (10 mu M). Input resistance, membrane potential, or firing threshold did not change during quinpirole effect, suggesting a presynaptic site of action for quinpirole in some but not all glutamatergic afferents that make contact on a single cell. The present experiments show that dopaminergic presynaptic modulation of glutamatergic transmission in the neostriatum does not affect all stimulated afferents, suggesting that it is selective towards some of them. This may control the quality and quantity of afferent flow upon neostriatal neurons. (C) 1997 Wiley-Liss, Inc. |
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| Keywords:
4-Aminopyridine dopamine neostriatum presynaptic modulation quinpirole synaptic transmission |
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| Times cited: 47 |
| Journal impact: 2.68 |
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