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[摘要]：Methylphenidate (MPD) modulates dopamine (DA) overflow in part by redistributing vesicle pools, a function shared by the presynaptic protein alpha-synuclein (alpha-syn). We suggest that alpha-syn modifies the effect of MPD on DA neurotransmission. The effect was studied in the dorsal striatum in wild-type mice and two mouse lines lacking alpha-syn by using in vivo voltammetry and microdialysis. MPD (1 mg/kg) attenuated evoked DA overflow only in mice lacking alpha-syn but produced a similar increase in the extracellular DA levels in all three lines. A kinetic analysis showed that MPD decreased DA release per stimulus pulse in alpha-syn-deficient mice but increased in wild-type mice. MPD blocked DA reuptake and produced a similar increase in the apparent affinity (K(m)) for DA reuptake in all three lines. Repeated-burst stimulation redistributes vesicular storage pools and facilitates DA overflow, and this form of facilitation is significantly enhanced in alpha-syn knockout mice. The DA reuptake inhibitor 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]4-(3-phenylpropyl)piperazine (GBR12909) (10 mg/kg) completely blocked the facilitation of DA overflow in all three lines, whereas MPD (1 mg/kg) selectively decreased it only in mice lacking alpha-syn. MPD (5 mg/kg) and GBR12909 (10 mg/kg) produced equipotent inhibition of DA reuptake (in terms of K(m)), indicating that reuptake inhibition does not explain the MPD selectivity. Our data indicate that MPD decreases DA release probability in the absence of alpha-syn and increases it in control animals, whereas the effect of MPD on DA reuptake is independent of alpha-syn. We suggest that this selectivity is based on alpha-syn-dependent compartmentalization of presynaptic DA. |
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