GABA_b受体在海马PP-DG习得性LTP中的调制作用

Modulatory role of GABA_b receptor in hippocampal learning-dependent LTP at PP-DG synapses in rat

应用慢性埋植电极技术以电生理结合行为学的方法 ,在大鼠明暗分辨学习中 ,于每实验日训练前给DG微量注射 GABAb 受体拮抗剂 saclofen1 μl,观察此处理对海马 DG突触效应及行为习得的影响 ,结果表明 :较高浓度 (50 μmol/L)的 saclofen对 DG突触效应的习得性长时程增强 (Long- term potentiation,LTP)的形成有明显的抑制性影响 ,相应地阻抑明暗分辨学习的习得 ;加快习得性 LTP的消退 ,使行为消退加速。较低浓度 (2 5μmol/L)的 saclofen却易化习得性 LTP的形成 ,加快条件反射的建立 ;延缓习得性 LTP及行为的消退。提示 GABAb 受体在海马 DG习得性 LTP的形成与保持中有重要的调制作用 。

The purpose of this study was to investigate the effects of microinjecting saclofen(50 μmol/L and 25 μmol/L),a selective GABA b receptor antagonist,into the DG region of the rat hippocampus on the synaptic efficacy and discrimination learning.The results showed that the development of learning dependent long term potentiation (LTP)in hippocampal DG was significantly depressed by microinjection of 50 μmol/L saclofen,and its extinction was accelerated.But,the microinjection of 25 μmol/L saclofen significantly facilitated the induction of learning dependent LTP,and its extinction was prolonged.Meanwhile,the establishment or extinction of conditioned response was correspondingly depressed or accelerated at higher(50 μmol/L)or lower (25 μmol/L)concentrations.It is suggested that GABA b receptor is involved in the formation and maintenance of learning dependent LTP,probably playing the modulatory role with different effect at higher or lower concentration.