Department of Neurobiology and Behavior, University of California Irvine, 1132 McGaugh Hall, Irvine, CA, 92697, USA.
Psychopharmacology (Berl). 2023 Oct;240(10):2101-2110. doi: 10.1007/s00213-023-06429-0. Epub 2023 Aug 2.
Designer receptors exclusively activated by designer drugs (DREADDs) are a tool for "remote control" of defined neuronal populations during behavior. These receptors are inert unless bound by an experimenter-administered designer drug, commonly clozapine-n-oxide (CNO). However, questions have emerged about the suitability of CNO as a systemically administered DREADD agonist.
Second-generation agonists such as JHU37160 (J60) have been developed, which may have more favorable properties than CNO. Here we sought to directly compare effects of CNO (0, 1, 5, & 10 mg/kg, i.p.) and J60 (0, 0.03, 0.3, & 3 mg/kg, i.p.) on operant food pursuit.
Male and female TH:Cre + rats and their wildtype (WT) littermates received cre-dependent hM4Di-mCherry vector injections into ventral tegmental area (VTA), causing inhibitory DREADD expression in VTA dopamine neurons of TH:Cre + rats. All rats were trained to stably lever press for palatable food on a fixed ratio 10 schedule, and doses of both agonists were tested on separate days in counterbalanced order.
All three CNO doses reduced operant rewards earned in rats with DREADDs, and no CNO dose had behavioral effects in WT controls. The highest J60 dose tested significantly reduced responding in DREADD rats, but this dose also increased responding in WTs, indicating non-specific effects. The magnitude of CNO and J60 effects in TH:Cre + rats were correlated and were present in both sexes.
Findings demonstrate the usefulness of directly comparing DREADD agonists when optimizing behavioral chemogenetics, and highlight the importance of proper controls, regardless of the DREADD agonist employed.
专门被设计药物激活的设计受体（DREADD）是在行为过程中对特定神经元群体进行“远程控制”的工具。这些受体只有在被实验者给予的设计药物（通常是氯氮平-N-氧化物，CNO）结合时才会起作用。然而，关于 CNO 作为一种系统性给予的 DREADD 激动剂的适用性问题已经出现。
已经开发出第二代激动剂，如 JHU37160（J60），它们可能具有比 CNO 更有利的特性。在这里，我们试图直接比较 CNO（0、1、5 和 10mg/kg，ip）和 J60（0、0.03、0.3 和 3mg/kg，ip）对操作性食物追求的影响。
雄性和雌性 TH：Cre+大鼠及其野生型（WT）同窝仔鼠接受 Cre 依赖性 hM4Di-mCherry 载体注射到腹侧被盖区（VTA），导致 TH：Cre+大鼠的 VTA 多巴胺神经元中抑制性 DREADD 表达。所有大鼠都接受了美味食物的固定比率 10 方案的稳定杠杆按压训练，并且在平衡的顺序下在不同的日子里测试了两种激动剂的剂量。
所有三种 CNO 剂量均减少了 DREADD 大鼠的操作性奖励，而没有 CNO 剂量对 WT 对照组产生行为影响。测试的最高 J60 剂量显著减少了 DREADD 大鼠的反应，但该剂量也增加了 WT 的反应，表明存在非特异性效应。在 TH：Cre+大鼠中，CNO 和 J60 作用的幅度相关，并且存在于两种性别中。
这些发现证明了在优化行为化学遗传学时直接比较 DREADD 激动剂的有用性，并强调了无论使用何种 DREADD 激动剂，适当控制的重要性。
