Biella G R, Spaiardi P, Jimenez-Moreno R, Magistretti J, Taglietti V, Toselli M
Department of Cellular and Molecular Physiological and Pharmacological Sciences, University of Pavia, Pavia, Italy.
Pflugers Arch. 2007 Dec;455(3):515-25. doi: 10.1007/s00424-007-0299-y. Epub 2007 Jul 19.
The perirhinal cortex (PRC) is a supra-modal cortical area that collects and integrates information originating from uni- and multi-modal neocortical regions, transmits it to the hippocampus, and receives a feedback from the hippocampus itself. The elucidation of the mechanisms that underlie the specific excitable properties of the different PRC neuronal types appears as an important step toward the understanding of the integrative functions of PRC. In this study, we investigated the biophysical properties of the transient, I (A)-type K(+) current recorded in pyramidal neurons acutely dissociated from layers II/III of PRC of the rat (P8-P16). The current activated at about -50 mV and showed a fast monoexponential decay (tau(h) >> 14 ms at -30 to +10 mV). I (A) recovery from inactivation also had a monoexponential time course. No significant differences in the biophysical properties or current density of I (A) were found in pyramidal neurons from rats of different ages. Application of 4-AP (1-5 mM) reversibly and selectively blocked I (A), and in current clamp conditions it increased spike duration and shortened the delay of the first spike during repetitive firing evoked by sustained depolarizing current injection. These properties are similar to those of the I (A) found in thalamic neurons and other cortical pyramidal neurons. Our results suggest that I (A) contributes to spike repolarization and to regulate both spike onset timing and firing frequency in PRC neurons.
嗅周皮质（PRC）是一个超模式皮质区域，它收集并整合来自单模式和多模式新皮质区域的信息，将其传输至海马体，并接收来自海马体自身的反馈。阐明不同PRC神经元类型特定兴奋性特性背后的机制，似乎是迈向理解PRC整合功能的重要一步。在本研究中，我们调查了从大鼠（P8 - P16）PRC的II/III层急性分离的锥体神经元中记录到的瞬时I（A）型钾电流的生物物理特性。该电流在约 -50 mV时激活，并表现出快速的单指数衰减（在 -30至 +10 mV时，τ(h) >> 14 ms）。I（A）从失活状态的恢复也具有单指数时间进程。在不同年龄大鼠的锥体神经元中，未发现I（A）的生物物理特性或电流密度有显著差异。应用4 - AP（1 - 5 mM）可可逆且选择性地阻断I（A），并且在电流钳制条件下，它会增加动作电位持续时间，并缩短在持续去极化电流注入诱发的重复放电期间第一个动作电位的延迟。这些特性与在丘脑神经元和其他皮质锥体神经元中发现的I（A）的特性相似。我们的结果表明，I（A）有助于动作电位复极化，并调节PRC神经元的动作电位起始时间和放电频率。
