Jo Y H, Stoeckel M E, Freund-Mercier M J, Schlichter R
Laboratoire de Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519-Centre National de la Recherche Scientifique, Université Louis Pasteur, 67084 Strasbourg Cedex, France.
J Neurosci. 1998 Apr 1;18(7):2377-86. doi: 10.1523/JNEUROSCI.18-07-02377.1998.
The functional characteristics of binding sites for the neuropeptide oxytocin (OT) detected by radioautography in laminae I and II of the dorsal horn (DH) and on cultured neonatal DH neurons were studied on the latter using perforated patch-clamp recordings. The neurons were identified by their spike discharge properties and on the basis of the presence of met-enkephalin-like and glutamate decarboxylase-like immunoreactivities. OT (100 nM) never induced any membrane current at a holding potential of -60 mV but increased the frequency of spontaneously occurring AMPA receptor-mediated EPSCs or the mean amplitude of electrically evoked EPSCs in a subset (35%) of neurons. The frequency of miniature EPSCs (m-EPSCs) recorded in the presence of 0.5 microM tetrodotoxin was also increased by OT (100 nM) without any change in their mean amplitude, indicating an action at a site close to the presynaptic terminal. The decay kinetics of any type of EPSC were never modified by OT. The effect of OT was reproduced by [Thr4, Gly7]-OT (100 nM), a selective OT receptor agonist, and blocked by d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH29]-ornithine vasotocin (100 nM), a specific OT receptor antagonist. Reducing the extracellular Ca2+ concentration from 2.5 to 0.3 mM in the presence of Cd2+ (100 microM) reversibly blocked the effect of OT on m-EPSCs. The OT receptors described here may represent the substrate for modulatory actions of descending hypothalamo-spinal OT-containing pathways on the nociceptive system.
采用穿孔膜片钳记录技术，研究了在背角（DH）I层和II层通过放射自显影检测到的神经肽催产素（OT）结合位点的功能特性，以及培养的新生DH神经元上的OT结合位点功能特性。根据神经元的放电特性以及甲硫氨酸脑啡肽样和谷氨酸脱羧酶样免疫反应性来识别神经元。在-60 mV的钳制电位下，OT（100 nM）从未诱导出任何膜电流，但在一部分（35%）神经元中增加了自发出现的AMPA受体介导的兴奋性突触后电流（EPSC）的频率或电诱发EPSC的平均幅度。在存在0.5 μM河豚毒素的情况下记录的微小EPSC（m-EPSC）频率也被OT（100 nM）增加，而其平均幅度没有任何变化，这表明OT作用于靠近突触前终末的位点。任何类型的EPSC的衰减动力学从未被OT改变。[Thr4, Gly7]-OT（100 nM）（一种选择性OT受体激动剂）可重现OT的作用，而d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH29]-鸟氨酸加压素（100 nM）（一种特异性OT受体拮抗剂）可阻断该作用。在存在Cd2+（100 μM）的情况下，将细胞外Ca2+浓度从2.5 mM降低到0.3 mM可可逆地阻断OT对m-EPSC的作用。这里描述的OT受体可能代表了下丘脑-脊髓含OT下行通路对伤害性系统调节作用的底物。
