Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico.
Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico.
Synapse. 2020 Aug;74(8):e22152. doi: 10.1002/syn.22152. Epub 2020 Mar 6.
Dopamine D R are widely expressed in basal ganglia where interact with D R. D R potentiate cAMP accumulation and GABA release stimulated by D R in striatonigral neurons through "atypical" signaling. During dopaminergic denervation, D R signaling changes to a "typical" in which antagonizes the effects of D R, the mechanisms of this switching are unknown. D nf splice variant regulates membrane anchorage and function of D R and decreases in denervation; thus, it is possible that D R signaling switching correlates with changes in D nf expression and increases of membranal D R that mask D R atypical effects. We performed experiments in unilaterally 6-hydroxydopamine lesioned rats and found a decrease in mRNA and protein of D nf, but not of D R in the denervated striatum. Proximity ligation assay showed that D R-D nf interaction decreased after denervation, whereas binding revealed an increased B in D R. The new D R antagonized cAMP accumulation and GABA release stimulated by D R; however, in the presence of N-Ethylmaleimide (NEM), to block G protein signaling, activation of D R produced its atypical signaling stimulating D R effects. Finally, we investigated if the typical and atypical effects of D R modulating GABA release are capable of influencing motor behavior. Injections of D R agonist into denervated nigra decreased D R agonist-induced turning behavior but potentiated it in the presence of NEM. Our data indicate the coexistence of D R typical and atypical signaling in striatonigral neurons during denervation that correlated with changes in the ratio of expression of D nf and D R isoforms. The coexistence of both atypical and typical signaling during denervation influences motor behavior.
多巴胺 D R 在基底神经节中广泛表达，与 D R 相互作用。D R 通过“非典型”信号增强 D R 刺激的纹状体苍白球神经元中 cAMP 的积累和 GABA 的释放。在多巴胺能神经支配丧失期间，D R 信号转导转变为“典型”，其中拮抗 D R 的作用，这种转换的机制尚不清楚。D nf 剪接变异体调节 D R 的膜锚定和功能，并且在去神经支配时减少；因此，D R 信号转导的转换可能与 D nf 表达的变化和膜 D R 的增加相关，后者掩盖了 D R 非典型作用。我们在单侧 6-羟多巴胺损伤大鼠中进行了实验，发现去神经支配的纹状体中 D nf 的 mRNA 和蛋白减少，但 D R 没有减少。接近连接测定显示去神经支配后 D R-D nf 相互作用减少，而结合显示 D R 的 B 增加。新的 D R 拮抗 D R 刺激的 cAMP 积累和 GABA 释放；然而，在存在 N-乙基马来酰亚胺（NEM）以阻断 G 蛋白信号的情况下，D R 的激活产生其非典型信号刺激 D R 效应。最后，我们研究了 D R 调节 GABA 释放的典型和非典型效应是否能够影响运动行为。将 D R 激动剂注入去神经支配的黑质减少了 D R 激动剂诱导的转动行为，但在存在 NEM 的情况下增强了它。我们的数据表明，在去神经支配期间，纹状体苍白球神经元中存在 D R 典型和非典型信号的共存，这与 D nf 和 D R 同工型表达比率的变化相关。去神经支配期间两种非典型和典型信号的共存会影响运动行为。
