大鼠边缘下区H2S/CBS在条件性恐惧消退保持中的作用及机制研究

Effect of infralimbic area H2S system on fear extinction of rats and its mechanism

目的探讨条件恐惧大鼠边缘下区胱硫醚-β-合成酶(cystathionine-β-synthase,CBS)/硫化氢(hydrogen sulfide,H2S)变化,及H2S对条件恐惧消退保持的作用及机制。方法采用以声音为提示的足底电击建立大鼠恐惧记忆模型,仅给予声音信号进行恐惧消退训练。Western blot和亚甲基蓝法检测边缘下区CBS/H2S含量,在体细胞外电生理技术记录边缘下区神经元放电情况。结果结果表明:(1)大鼠条件恐惧训练后边缘下区CBS/H2S含量减少(P<0.01),僵立行为加重(P<0.01);消退训练后边缘下区CBS/H2S含量有所回升(P<0.01,P<0.05),僵立行为有所减轻(P<0.01)。(2)外源性补充H2S后可改善消退训练大鼠的僵立行为(P<0.01)。(3)边缘下区微量压力注射硫化氢供体L-半胱氨酸使该区神经元自发放电频率升高(P<0.01)。结论边缘下区CBS/H2S参与调节恐惧记忆的消退过程,外源性增加H2S可增强条件恐惧消退行为,该作用可能与其增加边缘下区神经元放电频率和兴奋性有关。

Aim To explore the behavior and CBS/H2S levels in infralimbic(IL)medial prefrontal cortex(mPFC)in conditioned fear rats and study the effect of exogenous H2S on conditioned fear extinction of rats and the related mechanism.Methods The rat conditioned fear model was established with sound pairing with an aversive foot shock.Later the repeated single sound was used for extinction training.CBS/H2S content in IL tissues was measured using Western blot and methylene blue method.In vivo extracellular single unit recordings were used to examine the frequency of spontaneous discharges of IL neurons.Results 1.CBS/H2S level in IL tissues of conditioned fear model(control group)decreased(P<0.01)and the freezing level was aggravated(P<0.01),while after ex-tinction training CBS/H2S level increased(P<0.01,P<0.05)and the freezing level was alleviated(P<0.01).2.Freezing level decreased in NaHS group compared with extinction group(P<0.01).3.L-cysteine increased the frequency of spontaneous discharges of IL neurons(P<0.01).Conclusions Learning and memory ability decreases in PTSD model rats owing to the inhibition of CBS/H2S content in IL tissues.The mechanism of behavior improvement of H2S on PTSD model rats may be related to the excitation of H2S on frequency of spontaneous discharges of IL neurons.