The habenula is an epithalamic structure through which descending connections go from the telencephalon to the brainstem, putting it in a key location to provide feedback control over the ascending projections from the brainstem to the telencephalon. The medial habenula has a high concentration of nicotinic receptors. We assessed the role of medial habenular nicotinic receptors for nicotine self-administration (SA) in female young adult Sprague-Dawley rats. The rats had bilateral chronic infusion cannulae placed into the medial habenula nucleus. Each cannula was connected to a slow delivery osmotic minipump to chronically infuse mecamylamine (100 µg/side/day) or vehicle for four consecutive weeks. The rats were tested for nicotine SA for the first two weeks of mecamylamine infusion. Then, they had one week of enforced abstinence, during which they had no access to the nicotine SA. Finally, they had one week of resumed nicotine SA access. There was a significantly differential mecamylamine effects in animals with lower and higher pretreatment baseline nicotine SA. Rats with lower baseline nicotine SA levels showed a nearly significant mecamylamine-induced reduction in SA while those with higher baseline levels of SA showed a significant mecamylamine-induced increase in nicotine SA. This study determined that medial habenular nicotinic receptors are important for nicotine reinforcement. Baseline level of performance makes a crucial difference for the involvement of habenular mechanisms in nicotine reinforcement with nicotinic activation being important for maintaining nicotine self-administration for those with lower levels of baseline self-administration and the opposite effect with subjects with higher levels of baseline self-administration.

缰核是一种上丘脑结构，通过它下行连接从端脑到脑干，将其置于关键位置以提供对从脑干到端脑的上行投射的反馈控制。内侧缰核具有高浓度的烟碱受体. 我们评估了内侧缰核烟碱受体对雌性年轻成年 Sprague-Dawley 大鼠尼古丁自我给药 (SA) 的作用。将大鼠的双侧慢性输液套管置于内侧缰核中。每个插管都连接到一个缓慢输送的渗透微型泵，以连续四个星期长期注入美卡拉明（100 微克/侧/天）或载体。在输注美卡拉明的前两周，对大鼠进行尼古丁 SA 测试。然后，他们进行了一周的强制戒烟，在此期间他们无法使用尼古丁 SA。最后，他们恢复了一周的尼古丁 SA 访问。在预处理基线尼古丁 SA 较低和较高的动物中，美卡拉明的作用存在显着差异。基线尼古丁 SA 水平较低的大鼠显示美加明诱导的 SA 几乎显着减少，而基线 SA 水平较高的大鼠显示美加明诱导的尼古丁 SA 显着增加。这项研究确定内侧缰核烟碱受体对尼古丁强化很重要。基线表现水平对于缰核机制参与尼古丁强化具有至关重要的差异，尼古丁激活对于维持尼古丁自我管理对于基线自我管理水平较低的人来说很重要，而对于基线自我管理水平较高的受试者则相反-行政。这项研究确定内侧缰核烟碱受体对尼古丁强化很重要。基线表现水平对于缰核机制参与尼古丁强化具有至关重要的差异，尼古丁激活对于维持尼古丁自我管理对于基线自我管理水平较低的人来说很重要，而对于基线自我管理水平较高的受试者则相反-行政。这项研究确定内侧缰核烟碱受体对尼古丁强化很重要。基线表现水平对于缰核机制参与尼古丁强化具有至关重要的差异，尼古丁激活对于维持尼古丁自我管理对于基线自我管理水平较低的人来说很重要，而对于基线自我管理水平较高的受试者则相反-行政。