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VTA 神经元上β2 nAChR 的激活足以增强尼古丁在大鼠中的强化作用。

β2 nAChR Activation on VTA DA Neurons Is Sufficient for Nicotine Reinforcement in Rats.

机构信息

Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157.

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91106.

出版信息

eNeuro. 2023 May 25;10(5). doi: 10.1523/ENEURO.0449-22.2023. Print 2023 May.

Abstract

Mesolimbic nicotinic acetylcholine receptor (nAChRs) activation is necessary for nicotine reinforcement behavior, but it is unknown whether selective activation of nAChRs in the dopamine (DA) reward pathway is sufficient to support nicotine reinforcement. In this study, we tested the hypothesis that activation of β2-containing (β2*) nAChRs on VTA neurons is sufficient for intravenous nicotine self-administration (SA). We expressed β2 nAChR subunits with enhanced sensitivity to nicotine (referred to as β2Leu9'Ser) in the VTA of male Sprague Dawley (SD) rats, enabling very low concentrations of nicotine to selectively activate β2* nAChRs on transduced neurons. Rats expressing β2Leu9'Ser subunits acquired nicotine SA at 1.5 μg/kg/infusion, a dose too low to support acquisition in control rats. Saline substitution extinguished responding for 1.5 μg/kg/inf, verifying that this dose was reinforcing. β2Leu9'Ser nAChRs also supported acquisition at the typical training dose in rats (30 μg/kg/inf) and reducing the dose to 1.5 μg/kg/inf caused a significant increase in the rate of nicotine SA. Viral expression of β2Leu9'Ser subunits only in VTA DA neurons (via TH-Cre rats) also enabled acquisition of nicotine SA at 1.5 μg/kg/inf, and saline substitution significantly attenuated responding. Next, we examined electrically-evoked DA release in slices from β2Leu9'Ser rats with a history of nicotine SA. Single-pulse evoked DA release and DA uptake rate were reduced in β2Leu9'Ser NAc slices, but relative increases in DA following a train of stimuli were preserved. These results are the first to report that β2* nAChR activation on VTA neurons is sufficient for nicotine reinforcement in rats.

摘要

中脑边缘尼古丁乙酰胆碱受体 (nAChRs) 的激活对于尼古丁强化行为是必要的,但尚不清楚多巴胺 (DA) 奖励途径中 nAChRs 的选择性激活是否足以支持尼古丁强化。在这项研究中,我们检验了这样一个假设,即 VTA 神经元上包含β2 的 (β2*) nAChRs 的激活足以支持静脉内尼古丁自我给药 (SA)。我们在雄性 Sprague Dawley (SD) 大鼠的 VTA 中表达了对尼古丁敏感性增强的β2 nAChR 亚基(称为β2Leu9'Ser),使非常低浓度的尼古丁能够选择性地激活转导神经元上的β2* nAChRs。表达β2Leu9'Ser 亚基的大鼠以 1.5μg/kg/inf 的剂量获得尼古丁 SA,这个剂量太低以至于在对照大鼠中不能支持获得。盐水替代物使 1.5μg/kg/inf 的反应消退,验证了该剂量具有强化作用。β2Leu9'Ser nAChRs 也支持在大鼠的典型训练剂量(30μg/kg/inf)下获得,并且将剂量降低至 1.5μg/kg/inf 会导致尼古丁 SA 的速度显著增加。仅在 VTA DA 神经元中表达β2Leu9'Ser 亚基(通过 TH-Cre 大鼠)也使 1.5μg/kg/inf 的尼古丁 SA 获得成为可能,并且盐水替代物显著减弱了反应。接下来,我们检查了有尼古丁 SA 史的β2Leu9'Ser 大鼠切片中的电诱发 DA 释放。在β2Leu9'Ser NAc 切片中,单脉冲诱发的 DA 释放和 DA 摄取率降低,但刺激后 DA 的相对增加得到保留。这些结果是第一个报道 VTA 神经元上的β2* nAChR 激活足以在大鼠中增强尼古丁的结果。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/dbb8/10216253/289e2e88428f/ENEURO.0449-22.2023_f001.jpg

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