Tukker John J, Fuentealba Pablo, Hartwich Katja, Somogyi Peter, Klausberger Thomas
Medical Research Council Anatomical Neuropharmacology Unit, Oxford University, Oxford OX1 3TH, United Kingdom.
J Neurosci. 2007 Aug 1;27(31):8184-9. doi: 10.1523/JNEUROSCI.1685-07.2007.
Cortical gamma oscillations contribute to cognitive processing and are thought to be supported by perisomatic-innervating GABAergic interneurons. We performed extracellular recordings of identified interneurons in the hippocampal CA1 area of anesthetized rats, revealing that the firing patterns of five distinct interneuron types are differentially correlated to spontaneous gamma oscillations. The firing of bistratified cells, which target dendrites of pyramidal cells coaligned with the glutamatergic input from hippocampal area CA3, is strongly phase locked to field gamma oscillations. Parvalbumin-expressing basket, axo-axonic, and cholecystokinin-expressing interneurons exhibit moderate gamma modulation, whereas the spike timing of distal dendrite-innervating oriens-lacunosum moleculare interneurons is not correlated to field gamma oscillations. Cholecystokinin-expressing interneurons fire earliest in the gamma cycle, a finding that is consistent with their suggested function of thresholding individual pyramidal cells. Furthermore, we show that field gamma amplitude correlates with interneuronal spike-timing precision and firing rate. Overall, our recordings suggest that gamma synchronization in vivo is assisted by temporal- and domain-specific GABAergic inputs to pyramidal cells and is initiated in pyramidal cell dendrites in addition to somata and axon initial segments.
皮质γ振荡有助于认知加工，并且被认为由环绕胞体的GABA能中间神经元提供支持。我们对麻醉大鼠海马CA1区中已识别的中间神经元进行了细胞外记录，发现五种不同类型中间神经元的放电模式与自发γ振荡存在不同程度的相关性。双分层细胞靶向与来自海马CA3区的谷氨酸能输入对齐的锥体细胞树突，其放电与场γ振荡强烈锁相。表达小白蛋白的篮状细胞、轴-轴突细胞以及表达胆囊收缩素的中间神经元表现出适度的γ调制，而支配远端树突的腔隙-分子层中间神经元的放电时间与场γ振荡不相关。表达胆囊收缩素的中间神经元在γ周期中最早放电，这一发现与其对单个锥体细胞进行阈值调节的假定功能一致。此外，我们表明场γ振幅与中间神经元的放电时间精度和放电频率相关。总体而言，我们的记录表明，体内的γ同步由锥体细胞在时间和区域上特定的GABA能输入所辅助，并且除了胞体和轴突起始段之外，还在锥体细胞树突中起始。
