Department of Biological Sciences, Konkuk University, Seoul, South Korea.
Department of Biological Sciences, Konkuk University, Seoul, South Korea.
Behav Brain Res. 2021 Oct 11;415:113516. doi: 10.1016/j.bbr.2021.113516. Epub 2021 Aug 10.
Following the association of a neutral stimulus (conditioned stimulus, CS) with a biologically significant stimulus (unconditioned stimulus, US), CS-alone presentations generate extinction: a decline in the conditioned response. Many studies have revealed the neural substrates of fear extinction; however, a few have identified the brain regions responsible for appetitive extinction. Midbrain dopamine neurons are activated by presenting a reward or predictable reward cue, whereas the cue signaling the absence of reward activates the lateral habenula (LHb) neurons. We examined the engagement of the LHb in appetitive extinction. In the first phase, rats first received pairings of a CS (light) with US delivery (food pellets). In the second phase, rats in the CS-alone group underwent four CS-alone presentations, whereas those in the paired group received four pairings of light with food pellets. We also included a comparison group for CS-alone presentations: rats were placed in the training box without CS or US exposures in the first phase and received four CS-alone presentations in the second phase. Thirty minutes after the second phase, c-Fos levels in the ventral tegmental area (VTA), substantia nigra pars compacta (SNc), and LHb in these groups were measured. c-Fos levels in the LHb were higher in the paired-CS-alone group than in the paired-paired and comparison groups, while those in the VTA and SNc were significantly higher in the paired-paired group than in the other groups. On examination of LHb neurotoxic lesion effects on the decline of conditioned food-cup responses when a CS was repeatedly presented with no US, LHb lesions decelerated the decline in conditioned food-cup responses, suggesting a crucial role of LHb in appetitive extinction.
在中性刺激(条件刺激,CS)与生物意义上的刺激(非条件刺激,US)关联后,CS 单独呈现会产生消退:条件反应的下降。许多研究揭示了恐惧消退的神经基础;然而,只有少数研究确定了负责奖赏消退的大脑区域。中脑多巴胺神经元在呈现奖赏或可预测的奖赏线索时被激活,而提示没有奖赏的线索则激活外侧缰核(LHb)神经元。我们研究了 LHb 在奖赏消退中的参与情况。在第一阶段,大鼠首先接受 CS(光)与 US 传递(食物丸)的配对。在第二阶段,CS 单独组的大鼠接受了四次 CS 单独呈现,而配对组的大鼠则接受了四次 CS 与食物丸的配对呈现。我们还包括了 CS 单独呈现的对照组:在第一阶段,大鼠不接受 CS 或 US 暴露,放在训练箱中,在第二阶段接受四次 CS 单独呈现。第二阶段结束后 30 分钟,测量这些组的腹侧被盖区(VTA)、黑质致密部(SNc)和 LHb 中的 c-Fos 水平。配对 CS 单独组的 LHb 中的 c-Fos 水平高于配对配对组和对照组,而 VTA 和 SNc 中的 c-Fos 水平在配对配对组中明显高于其他组。当 CS 重复呈现而没有 US 时,LHb 神经毒性损伤对条件食物杯反应下降的影响的检查表明,LHb 在奖赏消退中起着关键作用。