School of Medicine and Psychology, Autonomous University of Baja California, Tijuana, Baja California 22427, México.
Department of Physiology, Faculty of Medicine, National Autonomous University of México, Mexico City 04510, México.
Learn Mem. 2021 Apr 15;28(5):153-161. doi: 10.1101/lm.053385.120. Print 2021 May.
In conditioned odor aversion (COA), the association of a tasteless odorized solution (the conditioned stimulus [CS]) with an intraperitoneal injection of LiCl (the unconditioned stimulus [US[), which produces visceral malaise, results in its future avoidance. The strength of this associative memory is mainly dependent on two parameters, that is, the strength of the US and the interstimuli interval (ISI). In rats, COA has been observed only with ISIs of ≤15 min and LiCl (0.15 M) doses of 2.0% of bodyweight, when tested 48 h after acquisition (long-term memory [LTM]). However, we previously reported a robust aversion in rats trained with ISIs up to 60 min when tested 4 h after acquisition (short-term memory [STM]). Since memories get reactivated during retrieval, in the current study we hypothesized that testing for STM would reactivate this COA trace, strengthening its LTM. For this, we compared the LTM of rats trained with long ISIs or low doses of LiCl initially tested for STM with that of rats tested for LTM only. Interestingly, rats conditioned under parameters sufficient to produce STM, but not LTM, showed a reliable LTM when first tested for STM. These observations suggest that under suboptimal training conditions, such as long ISIs or low US intensities, a CS-US association is established but requires reactivation in the short-term in order to persist in the long-term.
在条件性厌恶（COA）中，无味的调味溶液（条件刺激 [CS]）与腹腔内注射氯化锂（非条件刺激 [US]）的关联会导致内脏不适，从而导致其未来被回避。这种联想记忆的强度主要取决于两个参数，即 US 的强度和刺激间间隔（ISI）。在大鼠中，仅在 ISI≤15 分钟和腹腔注射氯化锂（0.15M）剂量为体重的 2.0%时，在获得后 48 小时（长时记忆 [LTM]）进行测试时，才会观察到 COA。然而，我们之前报道过在获得后 4 小时（短时记忆 [STM]）进行测试时，用长达 60 分钟的 ISI 训练的大鼠中会产生强烈的厌恶感。由于在检索过程中记忆会被重新激活，因此在当前研究中，我们假设对 STM 的测试会重新激活这种 COA 痕迹，从而增强其 LTM。为此，我们比较了最初接受 STM 测试的用长 ISI 或低剂量氯化锂训练的大鼠的 LTM，以及仅接受 LTM 测试的大鼠的 LTM。有趣的是，在足以产生 STM 的参数下进行训练的大鼠，但不能产生 LTM，当首次接受 STM 测试时，显示出可靠的 LTM。这些观察结果表明，在次优的训练条件下，例如长 ISI 或低 US 强度，会建立 CS-US 关联，但需要在短期内重新激活才能在长期内持续存在。
