Methadone maintenance treatment (MMT) is the most common treatment for opioid-dependent pregnant women worldwide. Despite its widespread use, MMT is associated with a variety of adverse neurodevelopmental outcomes in exposed offspring, particularly cognitive impairments. The neurobiological abnormalities underlying these cognitive impairments are, however, poorly understood. This is, in part, due to a lack of animal models that represents the standard of care that methadone is administered in the clinic, with inconsistencies in the timing, doses and durations of treatment. Here we describe the characterisation of a clinically relevant rat model of MMT in which the long-term behavioural and neurobiological effects of prenatal methadone exposure can be assessed in adolescent offspring. Female Sprague-Dawley rats were treated orally with an ascending methadone dosage schedule (5, 10, 15, 20, 25 and 30 mg/kg/day), self-administered in drinking water prior to conception, throughout gestation and lactation. Pregnancy success, maternal gestational weight gain, litter survival and size were not significantly altered in methadone-exposed animals. Methadone-exposed offspring body and brain weights were significantly lower at birth. Novel object recognition tests performed at adolescence revealed methadone-exposed offspring had impaired recognition memory. Furthermore, the rewarded T-maze alternation task demonstrated that methadone-exposed female, but not male, offspring also exhibit working memory and learning deficits. Immunoblots of the adolescent prefrontal cortex and hippocampus showed methadone-exposed offspring displayed reduced levels of mature BDNF, in addition to the GABAergic proteins, GAD67 and parvalbumin, in a sex- and brain region-specific fashion. This rat model closely emulates the clinical scenario in which methadone is administered to opioid-dependent pregnant woman and provides evidence MMT can cause cognitive impairments in adolescent offspring that may be underlined by perturbed neurodevelopment of the GABAergic system.

美沙酮维持治疗 (MMT) 是全球阿片类药物依赖孕妇最常见的治疗方法。尽管 MMT 被广泛使用，但 MMT 与暴露的后代的各种不良神经发育结果有关，特别是认知障碍。然而，人们对这些认知障碍背后的神经生物学异常知之甚少。这部分是由于缺乏代表美沙酮在临床上使用的护理标准的动物模型，治疗的时间、剂量和持续时间不一致。在这里，我们描述了一种临床相关的 MMT 大鼠模型的特征，其中可以在青春期后代中评估产前美沙酮暴露的长期行为和神经生物学影响。雌性 Sprague-Dawley 大鼠采用递增的美沙酮剂量方案（5、10、15、20、25 和 30 mg/kg/天）口服治疗，在受孕前、整个妊娠期和哺乳期在饮用水中自行给药。暴露于美沙酮的动物的妊娠成功率、孕期体重增加、产仔数和大小没有显着改变。暴露于美沙酮的后代体重和脑重在出生时显着降低。在青春期进行的新物体识别测试显示，暴露于美沙酮的后代识别记忆受损。此外，奖励 T 迷宫交替任务表明，暴露于美沙酮的雌性而非雄性后代也表现出工作记忆和学习缺陷。青少年前额叶皮层和海马体的免疫印迹显示，暴露于美沙酮的后代除了 GABAergic 蛋白、GAD67 和小白蛋白外，成熟 BDNF 水平降低，并且以性别和大脑区域特异性的方式。该大鼠模型密切模拟了将美沙酮用于阿片类药物依赖的孕妇的临床情况，并提供证据表明 MMT 可导致青春期后代的认知障碍，这可能会因 GABA 能系统的神经发育受到干扰而得到强调。