Background

Nicotine withdrawal syndrome is a major clinical problem. Animal models with sufficient predictive validity to support translation of pre-clinical findings to clinical research are lacking.

Aims

We evaluated the behavioural and neurochemical alterations in zebrafish induced by short- and long-term nicotine withdrawal.

Methods

Zebrafish were exposed to 1 mg/L nicotine for 2 weeks. Dependence was determined using behavioural analysis following mecamylamine-induced withdrawal, and brain nicotinic receptor binding studies. Separate groups of nicotine-exposed and control fish were assessed for anxiety-like behaviours, anhedonia and memory deficits following 2–60 days spontaneous withdrawal. Gene expression analysis using whole brain samples from nicotine-treated and control fish was performed at 7 and 60 days after the last drug exposure. Tyrosine hydroxylase (TH) immunoreactivity in pretectum was also analysed.

Results

Mecamylamine-precipitated withdrawal nicotine-exposed fish showed increased anxiety-like behaviour as evidenced by increased freezing and decreased exploration. ³H-Epibatidine labeled heteromeric nicotinic acethylcholine receptors (nAChR) significantly increased after 2 weeks of nicotine exposure while ¹²⁵I-αBungarotoxin labeled homomeric nAChR remained unchanged. Spontaneous nicotine withdrawal elicited anxiety-like behaviour (increased bottom dwelling), reduced motivation in terms of no preference for the enriched side in a place preference test starting from Day 7 after withdrawal and a progressive decrease of memory attention (lowering discrimination index). Behavioural differences were associated with brain gene expression changes: nicotine withdrawn animals showed decreased expression of chrna 4 and chrna7 after 60 days, and of htr2a from 7 to 60 days.The expression of c-Fos was significantly increased at 7 days. Finally, Tyrosine hydroxylase (TH) immunoreactivity increased in dorsal parvocellular pretectal nucleus, but not in periventricular nucleus of posterior tuberculum nor in optic tectum, at 60 days after withdrawal.

Conclusions

Our findings show that nicotine withdrawal induced anxiety-like behaviour, cognitive alterations, gene expression changes and increase in pretectal TH expression, similar to those observed in humans and rodent models.

中文翻译：

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斑马鱼和哺乳动物自发尼古丁戒断情绪样反应机制的保护

背景

尼古丁戒断综合征是一个主要的临床问题。缺乏具有足够预测有效性以支持将临床前发现转化为临床研究的动物模型。

目标

我们评估了短期和长期尼古丁戒断引起的斑马鱼行为和神经化学变化。

方法

斑马鱼暴露于 1 mg/L 尼古丁 2 周。使用美加明诱导戒断后的行为分析和脑烟碱受体结合研究确定依赖性。在自发戒断 2-60 天后，分别评估暴露于尼古丁的鱼和对照鱼的焦虑样行为、快感缺乏和记忆缺陷。在最后一次药物暴露后 7 天和 60 天使用来自尼古丁处理和对照鱼的全脑样本进行基因表达分析。还分析了 pretectum 中的酪氨酸羟化酶 (TH) 免疫反应性。

结果

美加明沉淀戒断尼古丁暴露的鱼表现出增加的焦虑样行为，这可以通过增加冻结和减少探索来证明。³ H-依匹巴替丁标记的异聚烟碱乙酰胆碱受体 (nAChR) 在尼古丁暴露 2 周后显着增加，而¹²⁵I-α银环蛇毒素标记的同型 nAChR 保持不变。自发的尼古丁戒断引起焦虑样行为（增加底部居住），在戒断后第 7 天开始的位置偏好测试中不偏好富集一侧的动机降低，并且记忆注意力逐渐降低（降低辨别指数）。行为差异与大脑基因表达变化有关：戒断尼古丁的动物在 60 天后表现出chrna 4 和chrna7以及htr2a的表达下降7～60天。第7天c-Fos的表达明显增加。最后，在停药后 60 天，背侧小细胞前顶核的酪氨酸羟化酶 (TH) 免疫反应性增加，但在后结节的脑室周围核和视顶盖中没有增加。

结论

我们的研究结果表明，尼古丁戒断会引起焦虑样行为、认知改变、基因表达变化和前盖体 TH 表达增加，这与在人类和啮齿动物模型中观察到的相似。