Opiol Hanna, Pavlovski Ilya, Michalik Mateusz, Mistlberger Ralph E
Department of Psychology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.
Department of Psychology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.
Behav Brain Res. 2015 May 1;284:42-50. doi: 10.1016/j.bbr.2015.02.003. Epub 2015 Feb 9.
Rats readily learn to anticipate a reward signaled by an external stimulus. Anticipatory behaviors evoked by conditioned stimuli include 50 kHz ultrasonic vocalizations (USVs), a proposed behavioral correlate of positive affect and activation of midbrain dopamine pathways. Rats can also anticipate a reward, such as food, provided once daily, without external cueing. Anticipation of a daily reward exhibits formal properties of a circadian rhythm. The neural circuits that regulate the timing and amplitude of these rhythms remain an open question, but evidence suggests a role for dopamine. To gain further insight into the neural and affective correlates of circadian food anticipatory rhythms, we made 2h and 24h USV recordings in rats fed 2h/day in the light period, a procedure that induces robust anticipation 2-3h before mealtime. Potential interactions between internal and external time cues in USV production were evaluated by inclusion of a 3 kHz tone 15 min before mealtime. Prior to scheduled feeding, spontaneous 50 kHz USVs were rare during the light period. During scheduled feeding, flat and frequency modulated (FM) 50kHz USVs occurred prior to and during mealtime. FM USVs were more closely related to anticipation, while flat USVs were more dependent on food access. USVs also occurred during spontaneous waking at other times of day. The tone did not evoke USVs but did modulate activity. Behavioral anticipation of a daily meal is accompanied by USVs consistent with a positive affective state and elevated dopamine transmission.
大鼠很容易学会预期由外部刺激所预示的奖励。条件刺激引发的预期行为包括50千赫兹的超声波发声（USV），这是一种被认为与积极情绪及中脑多巴胺通路激活相关的行为表现。大鼠也能够在没有外部提示的情况下预期每天提供一次的奖励，比如食物。对每日奖励的预期呈现出昼夜节律的形式特征。调节这些节律的时间和幅度的神经回路仍是一个悬而未决的问题，但有证据表明多巴胺发挥了作用。为了进一步深入了解昼夜食物预期节律的神经和情感关联，我们对在光照期每天进食2小时的大鼠进行了2小时和24小时的超声波发声记录，这一过程会在进餐前2 - 3小时引发强烈的预期。通过在进餐前15分钟加入3千赫兹的音调，评估了超声波发声产生过程中内部和外部时间线索之间的潜在相互作用。在预定喂食之前，光照期很少出现自发的50千赫兹超声波发声。在预定喂食期间，平稳的和调频的（FM）50千赫兹超声波发声在进餐前和进餐期间出现。调频超声波发声与预期的关系更为密切，而平稳的超声波发声则更依赖于食物获取。超声波发声在一天中的其他时间自发清醒时也会出现。音调不会引发超声波发声，但会调节活动。对每日一餐的行为预期伴随着与积极情感状态和多巴胺传递增强相一致的超声波发声。
