Calcium-dependent inhibition of synaptosomal serotonin transport by the α2-adrenoceptor agonist 5-bromo-N-[4,5-dihydro-1H-imidazol-2-yl]-6-quinoxalinamine (UK14304)
Calcium-dependent inhibition of synaptosomal serotonin transport by the α2-adrenoceptor agonist 5-bromo-N-[4,5-dihydro-1H-imidazol-2-yl]-6-quinoxalinamine (UK14304)
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DOI：
10.1124/jpet.102.047134
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发表时间：
2003-06-01
影响因子：
3.5
通讯作者：
Blakely, RD
中科院分区：
文献类型：
--
作者：
Ansah, TA;Ramamoorthy, S;Blakely, RD
终止多巴胺能传递是质膜5-羟色胺（5-羟色胺，5-HT）转运蛋白（SERT）的功能，该转运蛋白也是抗抑郁药、安非他明和可卡因的体内高亲和力靶点。研究表明，SERT是由蛋白激酶和磷酸酶连接的途径调节。相比之下，SERT的受体相关调节仅被最低限度地定义。由于去甲肾上腺素能刺激影响5-HT的释放，我们探讨了可能的突触前肾上腺素受体介导的调节SERT。在小鼠前脑突触体中，α（2）-肾上腺素受体激动剂，特别是5-溴-N-[4，5-二氢-1H-咪唑-2-基]-6-喹喔啉胺（UK 14304），触发了5-HT转运的浓度和时间依赖性降低。相反，5-HT摄取不受药理学α（1）-肾上腺素受体激活的影响。动力学上，UK 14304显着降低表观底物亲和力，Km，而不改变运输能力，V-max。在支持突触体中SERT最大抑制的UK 14304浓度下，未观察到对转染细胞中SERT的影响，表明UK 14304间接降低SERT活性。UK 14304对5-HT摄取的影响不被其他Na+和Cl-依赖性转运蛋白所共享。UK 14304介导的SERT功能的抑制是育亨宾敏感的，因为是由去甲肾上腺素引发的抑制，并在没有添加Ca 2+的情况下被废除。此外，电压敏感性Ca 2+通道拮抗剂减弱了UK 14304的作用，这与Ca 2+在UK 14304作用中的作用一致。与体外5-HT转运活性的改变一致，体内计时电流法研究表明，UK 14304显着延长5-HT清除。我们的研究结果表明，UK 14304调节SERT功能，在体外和体内通过信号转导途径，可能支持的钙离子通过电压敏感的钙离子通道流入。
Termination of serotonergic transmission is the function of the plasma membrane 5-hydroxytryptamine (serotonin, 5-HT) transporter (SERT), which is also a high-affinity target in vivo for antidepressants, amphetamines, and cocaine. Studies show that SERT is regulated by protein kinase- and phosphatase-linked pathways. In contrast, receptor-linked modulation of SERT is only minimally defined. Because noradrenergic stimulation is reported to influence 5-HT release, we explored possible presynaptic adrenoceptor-mediated regulation of SERT. In mouse forebrain synaptosomes, alpha(2)-adrenoceptor agonists, particularly 5-bromo-N-[4,5-dihydro-1H-imidazol-2-yl]-6-quinoxalinamine (UK14304), triggered a concentration- and time-dependent decrease in 5-HT transport. In contrast, 5-HT uptake was unaffected by pharmacological alpha(1)-adrenoceptor activation. Kinetically, UK14304 significantly decreased the apparent substrate affinity, K m without altering transport capacity, V-max. At concentrations of UK14304 supporting maximal inhibition of SERT in synaptosomes, no effect on SERT in transfected cells was observed, suggesting that UK14304 acts indirectly to reduce SERT activity. The effect of UK14304 on 5-HT uptake was not shared by other Na+ and Cl--dependent transporters. UK14304-mediated inhibition of SERT function was yohimbine-sensitive, as was inhibition triggered by norepinephrine, and was abolished in the absence of added Ca2+. Moreover, UK14304 effects were attenuated by voltage-sensitive Ca2+ channel antagonists, consistent with a role for Ca2+ in UK14304 effects. In agreement with altered 5-HT transport activity in vitro, in vivo chronoamperometry studies revealed that UK14304 significantly prolonged 5-HT clearance. Our findings suggest that UK14304 modulates SERT function in vitro and in vivo via signaling pathways, possibly supported by an influx of Ca2+ through voltage-sensitive Ca2+ channels.