Turel Zehra B, Prados Jose, Urcelay Gonzalo P
Department of Neuroscience, Psychology & Behaviour, University of Leicester, UK.
Department of Neuroscience, Psychology & Behaviour, University of Leicester, UK.
Behav Processes. 2020 Oct;179:104197. doi: 10.1016/j.beproc.2020.104197. Epub 2020 Jul 15.
In planarians, as seen in rodents, natural reinforcers (sucrose) and drugs of abuse support Conditioned Place Preference (CPP), which is a form of Pavlovian learning to examine the rewarding effects of natural reinforcers and drugs of abuse. Using this preparation, we have previously observed acquisition, extinction and reinstatement of sucrose CPP. In the present experiments, we used planaria to investigate the amnestic effects of Heat Shock (HS, a known stressor in planaria) following different amounts of CPP extinction sessions. Experiment 1 showed that planarians developed a CPP response to a sucrose-paired surface. Heat shock, when given in conjunction with exposure to the sucrose-paired surface, produced amnesia as assessed by a subsequent sucrose reinstatement test. We interpreted that the amnesic effect of HS was due to HS affecting the dominant excitatory memory at the time of HS exposure. Thus, we hypothesized that after extensive extinction training (10 exposures), HS would lead to recovery from extinction (when the new inhibitory memory is dominant at the time of HS exposure). Experiment 2 explored this possibility and showed that given HS following 10 extinction sessions had no amnestic effect on the excitatory CPP response. In Experiment 3, we hypothesized that 16 extinction sessions would produce a stronger (and hence dominant) extinction inhibitory trace, which then would be vulnerable to HS. We observed that HS impaired the expression of the extinction memory following 16 exposures. These results reveal different effects of HS on CPP memories depending on the amount of extinction, and are fully consistent with the literature using rodents and humans. In addition, they suggest that planaria is a promising pre-clinical model to assess fundamental memory processes.
在涡虫中，如同在啮齿动物中一样，天然强化物（蔗糖）和滥用药物支持条件性位置偏爱（CPP），这是一种巴甫洛夫式学习形式，用于研究天然强化物和滥用药物的奖赏效应。利用这种实验准备，我们之前观察到了蔗糖CPP的获得、消退和恢复。在本实验中，我们使用涡虫来研究不同次数的CPP消退训练后热休克（HS，涡虫中一种已知的应激源）的遗忘效应。实验1表明涡虫对与蔗糖配对的表面产生了CPP反应。当热休克与暴露于与蔗糖配对的表面同时进行时，通过随后的蔗糖恢复测试评估发现产生了遗忘。我们解释说，HS的遗忘效应是由于HS在暴露时影响了占主导地位的兴奋性记忆。因此，我们假设在广泛的消退训练（10次暴露）后，HS会导致从消退中恢复（当HS暴露时新的抑制性记忆占主导地位）。实验2探索了这种可能性，结果表明在10次消退训练后给予HS对兴奋性CPP反应没有遗忘效应。在实验3中，我们假设16次消退训练会产生更强（因此占主导地位）的消退抑制痕迹，然后该痕迹会易受HS影响。我们观察到在16次暴露后，HS损害了消退记忆的表达。这些结果揭示了HS对CPP记忆的不同影响取决于消退的次数，并且与使用啮齿动物和人类的文献完全一致。此外，它们表明涡虫是评估基本记忆过程的一个有前景的临床前模型。
