Rationale

Reward-associated cues can trigger incentive motivation for reward and invigorate reward-seeking behaviour via Pavlovian-to-instrumental transfer (PIT). Glutamate signaling within the basolateral amygdala (BLA) modulates cue-triggered increases in incentive motivation. However, the role of BLA metabotropic group II glutamate (mGlu_2/3) receptors is largely unknown.

Objectives

In Experiment 1, we characterized cue-triggered increases in incentive motivation for water reward using the PIT paradigm. In Experiment 2, we assessed the influence of intra-BLA microinjections of the mGlu_2/3 receptor agonist LY379268 on this effect.

Methods

Water-restricted male Sprague–Dawley rats learned to press a lever for water. Separately, they learned to associate one of two auditory cues with free water. On test days, rats could lever press under extinction conditions (no water), with intermittent, non-contingent CS+ and CS- presentations. In Experiment 1, rats were tested under baseline conditions. In Experiment 2, rats received intra-BLA microinjections of LY379268 (0, 3 and 6 \({\mu }\)g/hemisphere) before testing.

Results

Across experiments, CS+, but not CS-, presentations increased water-associated lever pressing during testing, even though responding was reinforced neither by water nor the CS+. Intra-BLA LY379268 abolished both CS+ potentiated pressing on the water-associated lever and CS+ evoked conditioned approach to the site of water delivery. LY379268 did not influence locomotion or instrumental and Pavlovian response rates during intervals between CS presentations or during the CS-, indicating no motor effects.

Conclusions

mGlu_2/3 receptor activity in the BLA mediates cue-triggered potentiation of incentive motivation for reward, suppressing both cue-induced increases in instrumental pursuit of the reward and anticipatory approach behaviour.

中文翻译：

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基底外侧杏仁核中的代谢组 II 谷氨酸受体介导线索触发的激励动机增加

基本原理

与奖励相关的线索可以通过巴甫洛夫到工具转移 (PIT) 触发奖励的激励动机并激发寻求奖励的行为。基底外侧杏仁核 (BLA) 内的谷氨酸信号调节提示触发的激励动机增加。然而，BLA 代谢型组 II 谷氨酸 (mGlu _2/3 ) 受体的作用在很大程度上是未知的。

目标

在实验 1 中，我们使用 PIT 范式描述了线索触发的水奖励激励动机增加。在实验 2 中，我们评估了 mGlu _2/3受体激动剂 LY379268的 BLA 内显微注射对此效果的影响。

方法

受水限制的雄性 Sprague-Dawley 大鼠学会了按杠杆取水。另外，他们学会了将两个听觉线索之一与自由水联系起来。在测试日，大鼠可以在灭绝条件下（无水）杠杆按压，间歇性、非偶然的 CS+ 和 CS- 演示。在实验 1 中，大鼠在基线条件下进行测试。在实验 2 中，大鼠在测试前接受了 BLA 内显微注射 LY379268（0、3 和 6 \({\mu}\) g/半球）。

结果

在整个实验中，CS+，而不是 CS-，在测试过程中增加了与水相关的杠杆压力，即使水和 CS+ 都没有增强响应。Intra-BLA LY379268 取消了 CS+ 对水相关杠杆的强化按压和 CS+ 诱发的到水输送部位的条件方法。在 CS 演示之间或 CS- 期间，LY379268 不影响运动或工具和巴甫洛夫反应率，表明没有运动影响。

结论

BLA 中的mGlu _2/3受体活性介导线索触发的奖励动机增强，抑制线索诱导的奖励性追求和预期接近行为的增加。