Giambalvo Cecilia T, Price Lawrence H
Rhode Island Psychiatric Research Center, Eleanor Slater Hospital, Cranston, Rhode Island 02920, USA.
Synapse. 2003 Dec 1;50(3):212-22. doi: 10.1002/syn.10262.
Fenfluramine releases serotonin (5-HT) via the 5-HT transporter (SERT). Previous work has shown that amphetamine increases particulate protein kinase C (PKC) activity in striatal synaptoneurosomes. The increased PKC activity is linked to the outward transport of dopamine, and when release is diminished, the inward transport of amphetamine inhibits PKC instead. Since there is homology among monoamine transporters, this study was undertaken to determine if D-fenfluramine has similar effects on PKC. The role of 5-HT receptors and endogenous 5-HT were also examined. Naive rats and rats pretreated with p-chlorophenylalanine (PCPA), a 5-HT synthesis inhibitor, were sacrificed. Cortical synaptoneurosomes were prepared and incubated with fenfluramine. PKC activity was determined by thiophosphorylation of endogenous substrates. It was found that 5-HT, D/L-fenfluramine, and D-fenfluramine increased PKC activity in a time- and dose-dependent manner. The 5-HT-mediated increase in PKC activity was attenuated by pretreatment with the 5-HT(2) antagonist ketanserin, but not with the SERT inhibitor fluoxetine. The D-fenfluramine-induced increase in PKC activity was completely prevented, however, by pretreatment with SERT inhibitors and partially with ketanserin. It was also attenuated by pretreatment with PCPA, resulting in a dose-dependent inhibition of PKC instead. Thus, when 5-HT release was diminished the uptake of D-fenfluramine inhibited PKC. Similar effects have been observed with amphetamine. Unlike D-fenfluramine, the D/L-fenfluramine-induced increase in PKC activity was partially resistant to PCPA pretreatment but was attenuated with bupropion, a dopamine transporter (DAT) inhibitor. SERT inhibitors (sertraline, paroxetine, citalopram, and fluoxetine) also increased PKC activity. Nefazodone and bupropion increased PKC activity, but mirtazapine was relatively inactive. The SERT inhibitor-induced increase in PKC was unaffected by pretreatment with PCPA but was inhibited by calcium. Similar effects on PKC activity have been observed with DAT inhibitors. These results, showing that D-fenfluramine altered PKC activity similar to D-amphetamine, suggest that the topographic homology between DAT and SERT may extend to their effects on PKC activity.
芬氟拉明通过5-羟色胺转运体（SERT）释放5-羟色胺（5-HT）。先前的研究表明，苯丙胺可增加纹状体突触体神经小体中的颗粒蛋白激酶C（PKC）活性。PKC活性的增加与多巴胺的外向转运有关，而当释放减少时，苯丙胺的内向转运则会抑制PKC。由于单胺转运体之间存在同源性，因此进行本研究以确定D-芬氟拉明对PKC是否有类似作用。同时也研究了5-HT受体和内源性5-HT的作用。处死未处理的大鼠和用5-HT合成抑制剂对氯苯丙氨酸（PCPA）预处理的大鼠。制备皮质突触体神经小体并与芬氟拉明一起孵育。通过内源性底物的硫代磷酸化来测定PKC活性。结果发现，5-HT、D/L-芬氟拉明和D-芬氟拉明均以时间和剂量依赖性方式增加PKC活性。5-HT介导的PKC活性增加可被5-HT（2）拮抗剂酮色林预处理减弱，但不能被SERT抑制剂氟西汀减弱。然而，SERT抑制剂预处理可完全阻止D-芬氟拉明诱导的PKC活性增加，酮色林预处理则部分阻止。PCPA预处理也可使其减弱，反而导致PKC的剂量依赖性抑制。因此，当5-HT释放减少时，D-芬氟拉明的摄取会抑制PKC。苯丙胺也观察到类似的作用。与D-芬氟拉明不同，D/L-芬氟拉明诱导的PKC活性增加对PCPA预处理有部分抗性，但可被多巴胺转运体（DAT）抑制剂安非他酮减弱。SERT抑制剂（舍曲林、帕罗西汀、西酞普兰和氟西汀）也增加PKC活性。奈法唑酮和安非他酮增加PKC活性，但米氮平相对无活性。SERT抑制剂诱导的PKC增加不受PCPA预处理影响，但受钙抑制。DAT抑制剂对PKC活性也观察到类似作用。这些结果表明，D-芬氟拉明改变PKC活性的方式与D-苯丙胺类似，提示DAT和SERT之间的拓扑同源性可能延伸至它们对PKC活性的影响。
