Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, FL, USA.
Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, FL, USA; Brain Institute, Florida Atlantic University, Jupiter, FL, 33458, USA.
Neurochem Int. 2019 Feb;123:59-68. doi: 10.1016/j.neuint.2018.05.013. Epub 2018 May 22.
The catecholamine neurotransmitter dopamine (DA) exerts powerful modulatory control of physiology and behavior across phylogeny. Perturbations of DA signaling in humans are associated with multiple neurodegenerative and behavioral disorders, including Parkinson's disease, attention-deficit/hyperactivity disorder, addiction and schizophrenia. In the nematode C. elegans, DA signaling regulates mating behavior, learning, food seeking and locomotion. Previously, we demonstrated that loss of function mutations in the dat-1 gene that encodes the presynaptic DA transporter (DAT-1) results in a rapid cessation of movement when animals are placed in water, termed Swimming Induced Paralysis (Swip). Loss of function mutations in genes that support DA biosynthesis, DA vesicular packaging and DA action at the extrasynaptic D2-type DA receptor DOP-3 suppress Swip in dat-1 animals, consistent with paralysis as arising from excessive DA signaling. Although animals grown on the vesicular monoamine transporter antagonist reserpine diminish Swip, the drug must be applied chronically, can impact the signaling of multiple biogenic amines, and has been reported to have penetrant, off-target actions. Here, we demonstrate that the antipsychotic drug azaperone potently and rapidly suppresses Swip behavior in either dat-1 mutants, as well as in wildtype animals treated with the DAT-1 antagonist nisoxetine, with genetic experiments consistent with DOP-3 antagonism as the mechanism of Swip suppression. Reversal of Swip in previously paralyzed dat-1 animals by azaperone application demonstrates an otherwise functionally-intact swimming circuit in these mutants. Finally, whereas azaperone suppresses DA-dependent Swip, the drug fails to attenuate the DA-independent paralysis induced by βPEA, aldicarb or genetic disruption of γ-aminobutyric acid (GABA) signaling. We discuss our findings with respect to the use of azaperone as a potent and selective tool in the identification and analysis of presynaptic mechanisms that regulate DA signaling.
儿茶酚胺神经递质多巴胺（DA）在整个进化过程中对生理和行为产生强大的调节控制。人类的 DA 信号转导紊乱与多种神经退行性和行为障碍有关，包括帕金森病、注意力缺陷/多动障碍、成瘾和精神分裂症。在秀丽隐杆线虫中，DA 信号调节交配行为、学习、觅食和运动。以前，我们证明了编码突触前多巴胺转运体（DAT-1）的 dat-1 基因的功能丧失突变会导致动物放入水中时快速停止运动，称为游泳诱导麻痹（Swip）。支持 DA 生物合成、DA 囊泡包装以及突触外 D2 型 DA 受体 DOP-3 处 DA 作用的基因的功能丧失突变会抑制 dat-1 动物中的 Swip，这与麻痹是由过度的 DA 信号引起的一致。尽管在含有囊泡单胺转运体拮抗剂利血平的培养基中生长的动物会减少 Swip，但该药物必须长期应用，会影响多种生物胺的信号转导，并且据报道具有穿透性、非靶向作用。在这里，我们证明抗精神病药物阿扎哌隆能够快速且强烈地抑制 dat-1 突变体或用 DAT-1 拮抗剂 nisoxetine 处理的野生型动物中的 Swip 行为，遗传实验结果与 DOP-3 拮抗作用作为 Swip 抑制的机制一致。阿扎哌隆在先前瘫痪的 dat-1 动物中逆转 Swip，证明了这些突变体中游泳回路功能完好。最后，尽管阿扎哌隆抑制了依赖 DA 的 Swip，但该药物不能减弱由βPEA、aldicarb 或 GABA 信号遗传中断引起的非依赖 DA 的麻痹。我们根据阿扎哌隆作为鉴定和分析调节 DA 信号的突触前机制的有效和选择性工具的用途讨论了我们的发现。
