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- In Vivo Two-Photon Imaging Reveals a Role of Arc in Enhancin...In Vivo Two-Photon Imaging Reveals a Role of Arc in Enhancing Orientation Specificity in Visual Cortex
Cell, Volume 126, Issue 2, 28 July 2006, Pages 389-402
Kuan Hong Wang, Ania Majewska, James Schummers, Brandon Farley, Chengcheng Hu, Mriganka Sur and Susumu Tonegawa
SummaryCortical representations of visual information are modified by an animal's visual experience. To investigate the mechanisms in mice, we replaced the coding part of the neural activity-regulated immediate early gene Arc with a GFP gene and repeatedly monitored visual experience-induced GFP expression in adult primary visual cortex by in vivo two-photon microscopy. In Arc-positive GFP heterozygous mice, the pattern of GFP-positive cells exhibited orientation specificity. Daily presentations of the same stimulus led to the reactivation of a progressively smaller population with greater reactivation reliability. This adaptation process was not affected by the lack of Arc in GFP homozygous mice. However, the number of GFP-positive cells with low orientation specificity was greater, and the average spike tuning curve was broader in the adult homozygous compared to heterozygous or wild-type mice. These results suggest a physiological function of Arc in enhancing the overall orientation specificity of visual cortical neurons during the post-eye-opening life of an animal.
Summary | Full Text | PDF (1004 kb) - Electrochemical Properties of Hydrated Cation-Selective Glas...Electrochemical Properties of Hydrated Cation-Selective Glass Membrane
Biophysical Journal, Volume 14, Issue 1, 1 January 1974, Pages 46-68
Chin Ok Lee and Harry A. Fozzard
AbstractElectrochemical properties of cation-selective glass microelectrodes made from NAS were studied. There was a marked fall in electrical resistance of the microelectrodes stored in 3 M KCl solution (aging). The resistance was in the range of 2×10 to 10 Ω, which were much lower than those estimated from the electrical resistivity of dry glass for the equivalent dimensions of microelectrode working tips. This fall in resistance was accompanied by an increase in microelectrode selectivity for K. The low resistance and increased K selectivity are desirable features that make the microelectrode more suitable for application to biologic studies. The changes in microelectrode resistance and selectivity were interpreted to be due to hydration of the entire thickness of the glass membrane, resulting in a change in the field strength of anionic sites and formation of ionic channels in the glass membrane. Thus, the fall in resistance is explained by decrease in energy barrier, which is equivalent to the activation energy of interaction between the cations and anionic sites in the glass membrane. Some of the microelectrodes showed a transient depolarization that resembled the action potential of a biological membrane. This transient depolarization was associated with the changes in microelectrode resistance and selectivity. The transient depolarizations suggest the temporary development of wide channels in the membrane permitting free movement of hydrated cations according to the bulk electrochemical gradient.
Abstract | PDF (1668 kb) - Intracellular microelectrode measurements in small cells eva...Intracellular microelectrode measurements in small cells evaluated with the patch clamp technique
Biophysical Journal, Volume 50, Issue 6, 1 December 1986, Pages 1203-1209
C. Ince, E. van Bavel, B. van Duijn, K. Donkersloot, A. Coremans, D.L. Ypey and A.A. Verveen
AbstractMicroelectrode penetration of small cells leads to a sustained depolarization of the resting membrane potential due to a transmembrane shunt resistance (Rs) introduced by the microelectrode. This has led to underestimation of the resting membrane potential of various cell types. However, measurement of the fast potential transient occurring within the first few milliseconds after microelectrode penetration can provide information about pre-impalement membrane electrophysiological properties. We have analyzed an equivalent circuit of a microelectrode measurement to establish the conditions under which the peak of the impalement transients (Ep) approaches the pre-impalement resting membrane potential (Em) of small cells most closely. The simulation studies showed that this is the case when the capacitance of the microelectrode is low and the membrane capacitance of the cell high. In experiments performed to assess the reliability of Ep as a measure of Em, whole-cell patch clamp measurements were performed in the current clamp mode to monitor, free from the effects of Rs, Em in cultured human monocytes. Microelectrode impalement of such patch clamped cells and measurement of Ep made it possible to detect correlation between Ep and Em and showed that for small cells such as human monocytes Ep is on average 6 mV less negative than the resting membrane potential.
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Copyright © 1983 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 42, Issue 2, 191-193, 1 May 1983
doi:10.1016/S0006-3495(83)84385-9
Brief Communications
A Note on the Reactivation of the Fast Sodium Current in Spherical Clusters of Embryonic Chick Heart Cells
L. Ebihara, N. Shigeto, M. Lieberman and E.A. Johnson
Abstract
Reactivation of the fast sodium current in spherical clusters of embryonic chick heart cells was studied using the two-microelectrode voltage-clamp technique. The results show that there are at least two phases of reactivation. The contribution of the two phases to the overall reactivation process is highly dependent on the particular pulse protocol used to measure them.
