The lateral habenula (LHb) balances reward and aversion by opposing activation of brain reward nuclei and is involved in the inhibition of responding for cocaine in a model of impulsive behavior. Previously, we reported that the suppression of cocaine seeking was prevented by LHb inactivation or nonselective antagonism of LHb mAChRs. Here, we investigate mAChR subtypes mediating the effects of endogenous acetylcholine in this model of impulsive drug seeking and define cellular mechanisms in which mAChRs alter LHb neuron activity. Using in vitro electrophysiology, we find that LHb neurons are depolarized or hyperpolarized by the cholinergic agonists oxotremorine-M (Oxo-M) and carbachol (CCh), and that mAChRs inhibit synaptic GABA and glutamatergic inputs to these cells similarly in male and female rats. Synaptic effects of CCh were blocked by the M₂-mAChR (M₂R) antagonist AFDX-116 and not by pirenzepine, an M₁-mAChR (M₁R) antagonist. Oxo-M-mediated depolarizing currents were also blocked by AFDX-116. Although M₂R activation inhibited excitatory and inhibitory inputs to LHb neurons, the effect on excitation was greater, suggesting a shift in excitatory-inhibitory balance toward net inhibition. Activation of VTA inhibitory inputs to LHb neurons, via channelrhodopsin-2 expression, evoked IPSCs that were inhibited by M₂Rs. Finally, we measured LHb-dependent operant response inhibition for cocaine and found it impaired by antagonism of M₂Rs, and not M₁Rs. In summary, we show that a cholinergic signal to LHb and activation of M₂Rs are critical to enable inhibition of responding for cocaine, and we define cellular mechanisms through which this may occur.

SIGNIFICANCE STATEMENT The lateral habenula (LHb) is a brain region receiving information from brain areas involved in decision-making, and its output influences motivation, reward, and movement. This interface between thoughts, emotions, and actions is how the LHb permits adaptive behavior, and LHb dysfunction is implicated in psychiatric and drug use disorders. Silencing the LHb impairs control over cocaine seeking in rats, and mAChRs are also implicated. Here, we measured cocaine seeking while blocking different mAChRs and examined mechanisms of mAChR effects on LHb neurons. M₂-mAChRs were necessary for control of cocaine seeking, and these receptors altered LHb neuron activity in several ways. Our study reveals that LHb M₂-mAChRs represent a potential target for treating substance use disorders.

外侧缰核 (LHb) 通过对抗大脑奖励核的激活来平衡奖励和厌恶，并参与抑制冲动行为模型中对可卡因的反应。以前，我们报道了 LHb 失活或 LHb mAChRs 的非选择性拮抗作用阻止了对可卡因寻求的抑制。在这里，我们研究了 mAChR 亚型在这种冲动性寻药模型中介导内源性乙酰胆碱的作用，并定义了 mAChR 改变 LHb 神经元活动的细胞机制。体外使用电生理学，我们发现 LHb 神经元被胆碱能激动剂氧代震颤素-M (Oxo-M) 和卡巴胆碱 (CCh) 去极化或超极化，并且 mAChRs 在雄性和雌性大鼠中类似地抑制这些细胞的突触 GABA 和谷氨酸能输入。CCh 的突触作用被 M ₂ -mAChR (M ₂ R) 拮抗剂 AFDX-116 阻断，而不是被 M ₁ -mAChR (M ₁ R) 拮抗剂哌仑西平阻断。Oxo-M 介导的去极化电流也被 AFDX-116 阻断。虽然 M ₂R 激活抑制 LHb 神经元的兴奋性和抑制性输入，对兴奋的影响更大，表明兴奋性抑制平衡向净抑制转变。通过 channelrhodopsin-2 表达激活 VTA 对 LHb 神经元的抑制性输入，诱发被 M ₂ Rs 抑制的 IPSC。最后，我们测量了可卡因的 LHb 依赖性操作反应抑制，发现它受到 M ₂ Rs 而非 M ₁ Rs 拮抗作用的损害。总之，我们表明 LHb 的胆碱能信号和 M ₂ Rs 的激活对于抑制对可卡因的反应至关重要，我们定义了可能发生这种情况的细胞机制。

意义声明外侧缰核 (LHb) 是一个大脑区域，它从参与决策的大脑区域接收信息，其输出影响动机、奖励和运动。思想、情绪和行动之间的这种界面是 LHb 允许适应性行为的方式，而 LHb 功能障碍与精神病和药物使用障碍有关。沉默 LHb 会削弱大鼠对寻找可卡因的控制，并且 mAChRs 也有牵连。在这里，我们在阻断不同的 mAChRs 的同时测量了可卡因寻求，并检查了 mAChR 对 LHb 神经元的影响机制。M ₂ -mAChRs 是控制可卡因寻找所必需的，这些受体以多种方式改变了 LHb 神经元的活动。我们的研究表明，LHb M ₂-mAChRs 代表了治疗物质使用障碍的潜在目标。