Carlson G C, Shipley M T, Keller A
Department of Anatomy, Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
J Neurosci. 2000 Mar 1;20(5):2011-21. doi: 10.1523/JNEUROSCI.20-05-02011.2000.
We investigated the mechanisms of long-lasting depolarizing potentials (LLDs) generated in mitral cells with whole-cell patch recordings in the rat olfactory bulb slice. LLDs occur spontaneously and are evoked by either orthodromic stimulation of the olfactory nerve or antidromic stimulation of mitral and tufted (M/T) cells. LLDs are followed by a long refractory period, limiting LLD generation to approximately 1 Hz. LLD production does not appear to involve either intrinsic voltage-activated or metabotropic mechanisms. The initiation of LLDs requires activation of non-NMDA but not NMDA receptors. Dual recordings from the apical dendrites and somata of mitral cells show that LLDs are generated in the distal portion of the apical dendrite, most likely in the glomerulus. The rising phase of LLDs shows characteristics of polyneuronal input, including a high variability and sensitivity to charge screening. Paired recordings from adjacent mitral cells suggest that LLDs occur synchronously only in cells whose apical dendrites ramify in the same glomerulus. These findings suggest that LLDs involve recurrent, intraglomerular dendrodendritic interactions among M/T cells.
我们采用全细胞膜片钳记录技术，在大鼠嗅球切片中研究了二尖瓣细胞产生长时程去极化电位（LLDs）的机制。LLDs可自发出现，也可由嗅神经的顺向刺激或二尖瓣和簇状（M/T）细胞的逆向刺激诱发。LLDs之后会有一个长的不应期，将LLDs的产生频率限制在约1Hz。LLDs的产生似乎不涉及内在电压激活机制或代谢型机制。LLDs的起始需要非NMDA受体而非NMDA受体的激活。对二尖瓣细胞顶树突和胞体的双记录显示，LLDs在顶树突的远端产生，最有可能在肾小球。LLDs的上升期表现出多神经元输入的特征，包括高变异性和对电荷筛选的敏感性。对相邻二尖瓣细胞的配对记录表明，LLDs仅在顶树突在同一肾小球分支的细胞中同步出现。这些发现表明，LLDs涉及M/T细胞之间反复的、肾小球内树突-树突相互作用。
