Melik E, Babar-Melik E, Ozgünen T, Binokay S
Division of Neurophysiology, Department of Physiology, Medical Faculty, Cukurova University, 01330 Balcali, Adana, Turkey.
Behav Brain Res. 2000 Jul;112(1-2):145-50. doi: 10.1016/s0166-4328(00)00175-3.
The brain serotonin is involved in mediation of emotional behaviour including anxiety and related fear conditioning. It is known that the median raphe nucleus (MRN) is the origin of a serotonergic pathway and mainly innervates septo-hippocampal formation which plays an important role in emotional cognition. However, its regulatory role in different types of fear conditioning is still unclear. In the present study, the animals underwent ibotenic acid or sham lesions of the median raphe nucleus and the effects of MRN lesions on immediate and delayed fear conditioning to multiple contextual cues were studied. Freezing behaviour served as a measure of contextual fear. Sham-lesioned animals showed reliable conditional freezing when observed immediately following foot-shock (1.0 mA) for 3-min test and 48 h after the shock for 12-min test. Rats with MRN lesions displayed robust freezing behaviour immediately after the shock, even though they showed a marked deficit in freezing 48 h following the shock. These findings indicate that the MRN-serotonergic septo-hippocampal pathway is involved in the regulation of anxiety related to fear conditioning triggered by contextual cues, suggesting that short-term contextual fear is independent on the MRN while long-term contextual fear depends on the MRN.
大脑5-羟色胺参与包括焦虑及相关恐惧条件反射在内的情绪行为调节。已知中缝核（MRN）是5-羟色胺能通路的起源，主要支配在情绪认知中起重要作用的隔区-海马结构。然而，其在不同类型恐惧条件反射中的调节作用仍不清楚。在本研究中，对动物进行中缝核的鹅膏蕈氨酸损伤或假损伤，并研究中缝核损伤对多种情境线索的即时和延迟恐惧条件反射的影响。僵住行为作为情境恐惧的指标。假损伤动物在足部电击（1.0 mA）后立即观察3分钟测试时以及电击后48小时进行12分钟测试时表现出可靠的条件性僵住。中缝核损伤的大鼠在电击后立即表现出强烈的僵住行为，尽管它们在电击后48小时的僵住行为明显不足。这些发现表明，中缝核-5-羟色胺能隔区-海马通路参与由情境线索触发的与恐惧条件反射相关的焦虑调节，提示短期情境恐惧独立于中缝核，而长期情境恐惧依赖于中缝核。
