Chang Stephen E, Smedley Elizabeth B, Stansfield Katherine J, Stott Jeffrey J, Smith Kyle S
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire 03755, and
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire 03755, and.
J Neurosci. 2017 Jun 7;37(23):5670-5680. doi: 10.1523/JNEUROSCI.2968-16.2017. Epub 2017 May 11.
Salt appetite, in which animals can immediately seek out salt when under a novel state of sodium deprivation, is a classic example of how homeostatic systems interface with learned associations to produce an on-the-fly updating of motivated behavior. Neural activity in the ventral pallidum (VP) has been shown to encode changes in the value of salt under such conditions, both the value of salt itself (Tindell et al., 2006) and the motivational value of its predictive cues (Tindell et al., 2009; Robinson and Berridge, 2013). However, it is not known whether the VP is necessary for salt appetite in terms of seeking out salt or consuming salt following sodium depletion. Here, we used a conditioned place-preference procedure to investigate the effects of optogenetically inhibiting the VP on context-driven salt seeking and the consumption of salt following deprivation. Male rats learned to associate one context with sucrose and another context with less-desirable salt. Following sodium depletion, and in the absence of either sucrose or salt, we found that inhibiting the VP selectively reduced the elevation in time spent in the salt-paired context. VP inhibition had minimal effects on the consumption of salt once it was made available. To our knowledge, this is the first evidence that the VP or any brain region is necessary for the ability to use contextual cues to guide salt seeking. These results highlight a dissociation between deficit-driven reward seeking and reward consumption to replenish those deficits, with the former process being particularly sensitive to on-line VP activity. Salt appetite, in which rats will immediately seek out a once-undesirable concentrated salt solution after being depleted of bodily sodium despite never having tasted salt as a positive reward, is a phenomenon showing how animals can update their motivational goals without any new learning or conditioning. This salt-seeking behavior is also observed when the animal is presented with salt-paired cues. The neural circuitry necessary for context-driven salt-seeking behavior is unknown. We used a novel conditioned place preference procedure to show that optogenetic inhibition of the ventral pallidum (VP), a region known for processing reward, impairs context-driven salt seeking and has minimal effects on the consumption of salt itself following sodium depletion. These results highlight the importance of the VP in context-driven reward-seeking behavior.
盐食欲是指动物在处于新的钠缺乏状态时能够立即寻找盐分的现象，它是体内平衡系统如何与习得关联相互作用以即时更新动机行为的经典例子。腹侧苍白球（VP）的神经活动已被证明在此类条件下能够编码盐的价值变化，包括盐本身的价值（廷德尔等人，2006年）及其预测线索的动机价值（廷德尔等人，2009年；罗宾逊和贝里奇，2013年）。然而，就钠缺乏后寻找盐分或摄入盐分而言，VP对于盐食欲是否必要尚不清楚。在此，我们使用条件性位置偏好程序来研究光遗传学抑制VP对情境驱动的盐寻找行为以及钠缺乏后盐摄入的影响。雄性大鼠学会将一种情境与蔗糖联系起来，将另一种情境与不太受欢迎的盐联系起来。在钠缺乏后，且在既没有蔗糖也没有盐的情况下，我们发现抑制VP会选择性地减少在与盐配对的情境中停留时间的增加。一旦盐可用，VP抑制对盐的摄入影响极小。据我们所知，这是第一个表明VP或任何脑区对于利用情境线索指导盐寻找能力是必要的证据。这些结果凸显了缺乏驱动的奖赏寻求与为补充这些缺乏而进行的奖赏消费之间的分离，前一过程对在线VP活动尤为敏感。盐食欲是指大鼠在身体钠耗尽后会立即寻找曾经不受欢迎的浓缩盐溶液，尽管它们从未将盐作为积极奖赏品尝过；这一现象展示了动物如何在没有任何新学习或条件作用的情况下更新其动机目标。当向动物呈现与盐配对的线索时也会观察到这种盐寻找行为。情境驱动的盐寻找行为所必需的神经回路尚不清楚。我们使用一种新的条件性位置偏好程序来表明，对以处理奖赏而闻名的腹侧苍白球（VP）进行光遗传学抑制会损害情境驱动的盐寻找行为，并且对钠缺乏后盐本身的摄入影响极小。这些结果凸显了VP在情境驱动的奖赏寻求行为中的重要性。
