小龙虾开肌神经肌肉接头单个释放位点处的GABAB受体激活可产生突触前抑制。

Activation of GABAB receptors at individual release boutons of the crayfish opener neuromuscular junction produces presynaptic inhibition.

Fischer Y, Parnas I

Otto Lowei Center for Cellular and Molecular Neurobiology, Department of Neurobiology, Hebrew University, Jerusalem, Israel.

J Neurophysiol. 1996 Apr;75(4):1377-85. doi: 10.1152/jn.1996.75.4.1377.

Abstract

Presynaptic inhibition in crustaceans involves the activation of gamma-aminobutyric acid-A (GABAA) receptors that produce an increase in chloride conductance at excitatory axon terminals. Such inhibition produced by single inhibitory pulses is blocked by picrotoxin, a GABAA antagonist. 2. Presynaptic inhibition produced by bath application of GABA was not blocked by picrotoxin. Measurements of the membrane resistance of the excitatory axon terminals revealed that substantial presynaptic inhibition still persisted after 50 microM picrotoxin had completely blocked the increase in conductance produced by 10 microM GABA. 3. Baclofen, a GABAB agonist, reduced release from the excitatory nerve terminals, and 20H-Saclofen, a GABAB antagonist, blocked the effect of baclofen and the presynaptic inhibition produced by 10 microM GABA. 4. 20H-Saclofen alone did not block presynaptic inhibition produced by 100 microM GABA, and the combined action of both 20H-Saclofen and picrotoxin was required to block such effects. 5. The excitatory nerve terminals seem to contain GABAA and GABAB receptors. The GABAB receptors are preferentially activated at lower GABA concentrations (in the microM range), whereas both the GABAA and GABAB receptors are activated at high GABA concentrations.

摘要

甲壳类动物的突触前抑制涉及γ-氨基丁酸-A（GABAA）受体的激活，该受体可使兴奋性轴突终末的氯离子电导增加。单个抑制性脉冲产生的这种抑制作用可被GABAA拮抗剂匹鲁卡品阻断。2. 浴加GABA产生的突触前抑制不被匹鲁卡品阻断。对兴奋性轴突终末膜电阻的测量显示，在50微摩尔匹鲁卡品完全阻断10微摩尔GABA产生的电导增加后，显著的突触前抑制仍然存在。3. GABAB激动剂巴氯芬减少了兴奋性神经终末的递质释放，GABAB拮抗剂20H-萨氯芬阻断了巴氯芬的作用以及10微摩尔GABA产生的突触前抑制。4. 单独使用20H-萨氯芬不能阻断100微摩尔GABA产生的突触前抑制，需要20H-萨氯芬和匹鲁卡品联合作用才能阻断这种效应。5. 兴奋性神经终末似乎含有GABAA和GABAB受体。GABAB受体在较低GABA浓度（微摩尔范围内）优先被激活，而GABAA和GABAB受体在高GABA浓度时均被激活。