Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, 405 30 Gothenburg, Sweden.
University of Maryland School of Medicine, 21201, Baltimore, Maryland, and.
J Neurosci. 2018 Jul 18;38(29):6597-6607. doi: 10.1523/JNEUROSCI.0071-18.2018. Epub 2018 Jun 25.
The prevalence of nicotine dependence is higher than that for any other substance abuse disorder; still, the underlying mechanisms are not fully established. To this end, we studied acute effects by nicotine on neurotransmission in the dorsolateral striatum, a key brain region with respect to the formation of habits. Electrophysiological recordings in acutely isolated brain slices from rodent showed that nicotine (10 nm to 10 μm) produced an LTD of evoked field potentials. Current-clamp recordings revealed no significant effect by nicotine on membrane voltage or action potential frequency, indicating that the effect by nicotine is primarily synaptic. Nicotine did not modulate sIPSCs, or the connectivity between fast-spiking interneurons and medium spiny neurons, as assessed by whole-cell recordings combined with optogenetics. However, the frequency of sEPSCs was significantly depressed by nicotine. The effect by nicotine was mimicked by agonists targeting α7- or α4-containing nAChRs and blocked in slices pretreated with a mixture of antagonists targeting these receptor subtypes. Nicotine-induced LTD was furthermore inhibited by dopamine D2 receptor antagonist and occluded by D2 receptor agonist. In addition, modulation of cholinergic neurotransmission suppressed the responding to nicotine, which might reflect upon the postulated role for nAChRs as a presynaptic filter to differentially govern dopamine release depending on neuronal activity. Nicotine-induced suppression of excitatory inputs onto medium spiny neurons may promote nicotine-induced locomotor stimulation and putatively initiate neuroadaptations that could contribute to the transition toward compulsive drug taking. To decrease smoking, prevalence factors that may contribute to the development of nicotine addiction need to be identified. The data presented here show that nicotine suppresses striatal neurotransmission by selectively reducing the frequency of excitatory inputs to medium spiny neurons (MSNs) while rendering excitability, inhibitory neurotransmission, and fast-spiking interneuron-MSN connectivity unaltered. In addition, we show that the effect displayed by nicotine outlasts the presence of the drug, which could be fundamental for the addictive properties of nicotine. Considering the inhibitory tone displayed by MSNs on dopaminergic cell bodies and local terminals, nicotine-induced long-lasting depression of striatal output could play a role in behavioral transformations associated with nicotine use, and putatively elicit neuroadaptations underlying compulsive drug-seeking habits.
尼古丁依赖的流行率高于任何其他物质滥用障碍;然而,其潜在机制尚未完全确定。为此,我们研究了尼古丁对背外侧纹状体神经传递的急性影响,背外侧纹状体是与习惯形成有关的关键脑区。来自啮齿动物急性分离脑片的电生理记录显示,尼古丁(10nm 至 10μm)产生了诱发电场电位的 LTD。电流钳记录显示,尼古丁对膜电压或动作电位频率没有显著影响,表明尼古丁的作用主要是突触的。尼古丁没有调制 sIPSCs,或通过全细胞记录结合光遗传学评估的快速发射中间神经元和中间神经元之间的连接。然而,sEPSC 的频率被尼古丁显著抑制。尼古丁的作用被靶向包含α7 或α4 的 nAChR 的激动剂模拟,并在用靶向这些受体亚型的混合物拮抗剂预处理的切片中被阻断。尼古丁诱导的 LTD 还被多巴胺 D2 受体拮抗剂抑制,并被 D2 受体激动剂阻断。此外,胆碱能神经传递的调制抑制了对尼古丁的反应,这可能反映了 nAChR 作为一种突触前滤波器的假设作用,根据神经元活动的不同来调节多巴胺的释放。尼古丁诱导的对中间神经元兴奋性输入的抑制可能促进尼古丁诱导的运动刺激,并可能引发神经适应,从而有助于向强迫性药物使用的转变。为了减少吸烟,需要确定可能导致尼古丁成瘾发展的流行因素。这里呈现的数据表明,尼古丁通过选择性地降低中间神经元(MSNs)兴奋性输入的频率来抑制纹状体神经传递,同时保持兴奋性、抑制性神经传递和快速发射中间神经元-MSN 连接不变。此外,我们表明,尼古丁的作用持续存在于药物存在之外,这对于尼古丁的成瘾特性可能是基本的。考虑到 MSNs 对多巴胺能细胞体和局部末端的抑制性张力,尼古丁诱导的纹状体输出的持久抑制可能在与尼古丁使用相关的行为转变中发挥作用,并可能引发强迫性觅药习惯的神经适应。