Samulack D D, Williams S, Lacaille J C
Département de physiologie, Université de Montréal, Canada.
Hippocampus. 1993 Jul;3(3):331-44. doi: 10.1002/hipo.450030308.
To examine the inhibitory postsynaptic potentials (IPSPs) elicited in pyramidal cells by interneurons situated at the stratum oriens/alveus border (O/A), glutamate was applied by micropressure to this area during intracellular recordings from CA1 pyramidal cells. Glutamate stimulation evoked IPSPs (glut-IPSPs) of small amplitude (4 mV), delayed peak latency (100-110 ms), and long duration (300-400 ms). Recurrent activation of interneurons via glutamate stimulation of pyramidal cells by local application in stratum pyramidale (PYR) evoked recurrent IPSPs (PYR glut-IPSPs) with similar amplitude and time course as O/A glut-IPSPs. The mean equilibrium potential of O/A glut-IPSPs (-77 mV) was significantly different from that of the PYR glut-IPSPs (-71 mV), however, neither equilibrium potential was significantly different from that of the electrically evoked early IPSP in the same cells. Glutamate-evoked IPSPs elicited from O/A displayed some response reversal (27% reversal) like those evoked from PYR (41% reversal). The early IPSP evoked by electrical stimulation displayed significantly more response reversal (67% reversal) than glut-IPSPs. Both types of glut-IPSPs (O/A and PYR) were associated with moderate increases in membrane conductance (5.9 and 6.6 nS, respectively), which were significantly less than the conductance change associated with the early IPSP (45.8 nS). In interneurons within PYR, glutamate stimulation in PYR readily elicited a flurry of excitatory postsynaptic potentials, whereas glutamate stimulation in O/A elicited IPSPs. The electrophysiological properties of IPSPs elicited in pyramidal cells by glutamate stimulation of interneurons in O/A were similar to those of recurrent IPSPs evoked from PYR. Given that both of these types of glutamate-evoked IPSPs were mostly mediated via GABAA receptor channels (Samulack DD, Lacaille J-C, 1993, Hippocampus 3:345-358), the small differences observed between equilibrium potentials, response reversals, and conductance changes could be due to a more electronically distant location from the soma of the synapses involved in O/A glut-IPSPs as compared to those of recurrent IPSPs elicited from PYR.
为了研究位于海马体原层/肺泡边界（O/A）的中间神经元在锥体细胞中引发的抑制性突触后电位（IPSPs），在对CA1锥体细胞进行细胞内记录期间，通过微压将谷氨酸施加到该区域。谷氨酸刺激诱发了小幅度（4 mV）、延迟峰值潜伏期（100 - 110毫秒）和长时间（300 - 400毫秒）的IPSPs（谷氨酸诱发的IPSPs，简称glut - IPSPs）。通过在锥体层（PYR）局部应用谷氨酸刺激锥体细胞来反复激活中间神经元，诱发了与O/A glut - IPSPs具有相似幅度和时间进程的反复性IPSPs（PYR谷氨酸诱发的IPSPs，简称PYR glut - IPSPs）。然而，O/A glut - IPSPs的平均平衡电位（-77 mV）与PYR glut - IPSPs的平均平衡电位（-71 mV）显著不同，不过，这两种平衡电位与同一细胞中电诱发的早期IPSP的平衡电位均无显著差异。从O/A诱发的谷氨酸诱发的IPSPs表现出一些反应反转（27%反转），与从PYR诱发的情况类似（41%反转）。电刺激诱发的早期IPSP表现出比glut - IPSPs显著更多的反应反转（67%反转）。两种类型的glut - IPSPs（O/A和PYR）均伴随着膜电导的适度增加（分别为5.9和6.6纳西门子），这显著小于与早期IPSP相关的电导变化（45.8纳西门子）。在PYR内的中间神经元中，PYR中的谷氨酸刺激很容易诱发一连串的兴奋性突触后电位，而O/A中的谷氨酸刺激则诱发IPSPs。通过O/A中的中间神经元谷氨酸刺激在锥体细胞中诱发的IPSPs的电生理特性与从PYR诱发的反复性IPSPs相似。鉴于这两种类型的谷氨酸诱发的IPSPs大多是通过GABAA受体通道介导的（Samulack DD，Lacaille J - C，1993年，《海马体》3：345 - 358），观察到的平衡电位、反应反转和电导变化之间的微小差异可能是由于与从PYR诱发的反复性IPSPs相比，参与O/A glut - IPSPs的突触离胞体的电子距离更远。
