Jhuang Yi-Ci, Chang Chun-Hui
Institute of Systems Neuroscience, National Tsing Hua University, Hsinchu 30013, Taiwan.
Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan.
Cereb Cortex. 2023 Mar 21;33(7):3498-3510. doi: 10.1093/cercor/bhac287.
The nucleus reuniens (RE) and the perirhinal cortex (PRC) are two major relay stations that interconnect the hippocampus (HPC) and the medial prefrontal cortex (mPFC). Previous studies have shown that both the RE and the PRC are involved in the acquisition of trace fear conditioning. However, the respective contribution of the two regions is unclear. In this study, we used pharmacological approach to compare their roles. Our data suggested that inactivation of the RE or the PRC during conditioning partially impaired, whereas inactivation of both areas totally abolished, the encoding of trace fear. We next examined whether the impaired encoding of trace fear under RE inactivation can be rescued with enhanced cholinergic tone in the PRC, and vice versa. Against our hypothesis, regardless of whether the RE was on-line or not, animals failed to encode trace fear when further engaging cholinergic activities in the PRC. Conversely, depending on PRC activation level during conditioning, further recruiting cholinergic activities in the RE led to a down-shift of fear response during retrieval. Our results revealed that the RE and the PRC were necessary for the encoding of trace fear. Moreover, there was differential importance of cholinergic modulation during the process.
reuniens核（RE）和嗅周皮质（PRC）是连接海马体（HPC）和内侧前额叶皮质（mPFC）的两个主要中继站。先前的研究表明，RE和PRC都参与了痕迹恐惧条件反射的习得。然而，这两个区域各自的作用尚不清楚。在本研究中，我们采用药理学方法来比较它们的作用。我们的数据表明，在条件反射过程中RE或PRC失活会部分损害痕迹恐惧的编码，而两个区域同时失活则会完全消除痕迹恐惧的编码。接下来，我们研究了在PRC中增强胆碱能张力是否可以挽救RE失活时受损的痕迹恐惧编码，反之亦然。与我们的假设相反，无论RE是否处于激活状态，当进一步激活PRC中的胆碱能活动时，动物都无法编码痕迹恐惧。相反，根据条件反射过程中PRC的激活水平，在RE中进一步募集胆碱能活动会导致检索过程中恐惧反应的下调。我们的结果表明，RE和PRC是痕迹恐惧编码所必需的。此外，在这个过程中胆碱能调制的重要性存在差异。
