Soltesz I, Bourassa J, Deschênes M
Centre de Recherche en Neurobiologie, Université Laval, Québec, Canada.
Neuroscience. 1993 Dec;57(3):555-64. doi: 10.1016/0306-4522(93)90005-z.
Intracellular current clamp recordings were obtained from mossy cells (n = 6, identified by intracellular injection of biocytin) of the dorsal dentate gyrus from rats under ketamine-xylazine anesthesia. During electroencephalographic theta rhythm (4-6 Hz), recorded with a macroelectrode placed in the contralateral dorsal hippocampus near the fissure, mossy cells displayed intracellular membrane potential oscillations at low frequencies (4-6 Hz) which appeared to be phase locked to the electroencephalographic theta rhythm. The frequency of the intracellular theta rhythm was independent of the membrane potential. However, the phase difference between the intracellular and the electroencephalographic theta rhythms as well as the amplitude of the intracellular theta oscillations were voltage-dependent. These findings are consistent with the hypothesis that rhythmic GABAA receptor-mediated inhibitory postsynaptic potentials contribute to the genesis of the intracellular theta rhythm. Indeed, mossy cells displayed an early, fast inhibitory postsynaptic potential in response to electrical stimulation of the entorhinal cortex, which most likely represents a GABAA receptor-mediated event, indicating that mossy cells possess functional GABAA receptors. At the resting membrane potential, mossy cells did not fire at each cycle of the electroencephalographic theta rhythm but fired only rarely (< 1 Hz). However, when they did fire they did so preferentially in phase with the peak positivity of the electroencephalographic theta rhythm. Reconstruction of two mossy cells with axonal projections to the inner molecular layer showed that the spatial extent of the influence such weakly discharging mossy cells may have on other dentate gyrus neurons during theta oscillations can be several millimeters in the septotemporal direction. In conclusion, these findings show that mossy cells of the rat hilus during ketamine-xylazine anesthesia participate in theta oscillations of the hippocampal formation, during which their low-frequency firing may contribute to the phase-locking of a large number of spatially distributed postsynaptic neurons with postsynaptic sites in the inner molecular layer of the dentate gyrus.
在氯胺酮-赛拉嗪麻醉下，从大鼠背侧齿状回的苔藓细胞（n = 6，通过细胞内注射生物素鉴定）获得细胞内电流钳记录。在使用放置在对侧背侧海马靠近裂隙处的宏观电极记录的脑电图θ节律（4-6Hz）期间，苔藓细胞表现出低频（4-6Hz）的细胞内膜电位振荡，这似乎与脑电图θ节律锁相。细胞内θ节律的频率与膜电位无关。然而，细胞内和脑电图θ节律之间的相位差以及细胞内θ振荡的幅度是电压依赖性的。这些发现与以下假设一致，即节律性GABAA受体介导的抑制性突触后电位有助于细胞内θ节律的产生。事实上，苔藓细胞对内嗅皮质的电刺激表现出早期、快速的抑制性突触后电位，这很可能代表GABAA受体介导的事件，表明苔藓细胞具有功能性GABAA受体。在静息膜电位时，苔藓细胞在脑电图θ节律的每个周期并不放电，而是很少放电（<1Hz）。然而，当它们放电时，它们优先在脑电图θ节律的正峰值相位放电。对两个向分子内层有轴突投射的苔藓细胞进行重建显示，在θ振荡期间，这种弱放电的苔藓细胞对其他齿状回神经元可能产生影响的空间范围在颞隔方向上可达数毫米。总之，这些发现表明，在氯胺酮-赛拉嗪麻醉期间，大鼠齿状回门区的苔藓细胞参与海马结构的θ振荡，在此期间它们的低频放电可能有助于大量空间分布的突触后神经元与齿状回分子内层的突触后位点进行锁相。
