Lawson Kate A, Ruiz Christina M, Mahler Stephen V
Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA USA.
bioRxiv. 2023 Mar 27:2023.03.27.534429. doi: 10.1101/2023.03.27.534429.
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, most 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 in TH:Cre+ rats. 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 a counterbalanced order.
All three CNO doses reduced operant food seeking in rats with DREADDs, and no CNO dose had behavioral effects in WT controls. The highest tested J60 dose significantly reduced responding in DREADD rats, but this dose also 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.
仅由设计药物激活的定制受体（DREADDs）是一种在行为过程中对特定神经元群体进行“远程控制”的工具。这些受体是无活性的，除非被实验者给予的设计药物（最常见的是氯氮平 - N - 氧化物，CNO）结合。然而，关于CNO作为全身给药的DREADD激动剂的适用性出现了一些问题。
已开发出第二代激动剂，如JHU37160（J60），其可能具有比CNO更有利的特性。在这里，我们试图直接比较CNO（0、1、5和10毫克/千克，腹腔注射）和J60（0、0.03、0.3和3毫克/千克，腹腔注射）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）同窝仔鼠接受了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。大鼠被训练在固定比例10的时间表上稳定地按压杠杆以获取美味食物，两种激动剂的剂量在不同的日子以平衡的顺序进行测试。
所有三种CNO剂量均降低了具有DREADDs的大鼠的操作性食物寻求行为，并且没有CNO剂量在WT对照中产生行为影响。测试的最高J60剂量显著降低了DREADD大鼠的反应，但该剂量也对WT大鼠产生反应，表明存在非特异性影响。TH:Cre +大鼠中CNO和J60效应的大小相关，并且在两性中均存在。
研究结果表明，在优化行为化学遗传学中直接比较DREADD激动剂是有用的，并强调了适当对照的重要性，无论使用何种DREADD激动剂。
