Minneci Federico, Janahmadi Mahyar, Migliore Michele, Dragicevic Natasa, Avossa Daniela, Cherubini Enrico
Neuroscience Programme, International School for Advanced Studies, Trieste, Italy.
Hippocampus. 2007;17(7):538-53. doi: 10.1002/hipo.20291.
GABAergic interneurons constitute a heterogeneous group of cells that exert a powerful control on network excitability and are responsible for the oscillatory behavior crucial for information processing in the brain. These cells have been differently classified according to their morphological, neurochemical, and physiological characteristics. Here, whole cell patch clamp recordings were used to further characterize, in transgenic mice expressing EGFP in a subpopulation of GABAergic interneurons containing somatostatin (GIN mice), the functional properties of EGFP-positive cells in stratum oriens of the CA1 region of the hippocampus, in slice cultures obtained from P8 old animals. These cells showed passive and active membrane properties similar to those found in stratum oriens interneurons projecting to stratum lacunosum-moleculare. Moreover, they exhibited different firing patterns that were maintained upon membrane depolarization: irregular (48%), regular (30%), and clustered (22%). Trains of action potentials in interneurons evoked in a minority of principal cells (3/45) small amplitude GABAergic currents that at 20 Hz underwent short-term depression. In contrast, excitatory connections between principal cells and EGFP-positive interneurons were highly reliable (17/55) and exhibited a frequency and use-dependent facilitation particularly in the gamma band. In addition, recordings from paired of interconnected EGFP-positive cells revealed in 47% of the cases electrical coupling, which was abolished by carbenoxolone (200 microM). On average, the coupling coefficient was 0.21 +/- 0.07. When electrical coupling was particularly strong it acted as a powerful low-pass filter, thus contributing to alter the output of individual cells. In conclusion, it appears that the dynamic interaction between cells with various firing patterns could differently affect GABAergic signaling, leading, as suggested by simulation data, to a wide range of interneuronal communication within the hippocampal network.
γ-氨基丁酸能中间神经元构成了一组异质性细胞，它们对网络兴奋性施加强大控制，并负责对大脑信息处理至关重要的振荡行为。这些细胞已根据其形态、神经化学和生理特征进行了不同分类。在这里，使用全细胞膜片钳记录进一步表征了在含有生长抑素的γ-氨基丁酸能中间神经元亚群中表达增强绿色荧光蛋白（EGFP）的转基因小鼠（GIN小鼠）海马体CA1区海马伞的EGFP阳性细胞的功能特性，这些切片培养物取自出生后8天的老龄动物。这些细胞表现出与投射到腔隙-分子层的海马伞中间神经元相似的被动和主动膜特性。此外，它们表现出不同的放电模式，这些模式在膜去极化时得以维持：不规则（48%）、规则（30%）和簇状（22%）。少数主细胞（3/45）诱发的中间神经元动作电位串引发了小幅度γ-氨基丁酸能电流，该电流在20 Hz时出现短期抑制。相比之下，主细胞与EGFP阳性中间神经元之间的兴奋性连接高度可靠（17/55），并表现出频率和使用依赖性促进作用，特别是在γ频段。此外，对成对的相互连接EGFP阳性细胞的记录显示，47%的情况下存在电耦合，这种耦合被羧苄青霉素（200 μM）消除。平均而言，耦合系数为0.21±0.07。当电耦合特别强时，它充当强大的低通滤波器，从而有助于改变单个细胞的输出。总之，似乎具有各种放电模式的细胞之间的动态相互作用可能会以不同方式影响γ-氨基丁酸能信号传导，正如模拟数据所表明的那样，导致海马网络内广泛的中间神经元通信。
