Concentration dynamics of nitric oxide in rat hippocampal subregions evoked by stimulation of the NMDA glutamate receptor
Authors: Ledo Ana , Barbosa Rui M. , Gerhardt Greg A. , Cadenas Enrique , Laranjinha João 
Published: November 2005

Nitric oxide (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}) production in response to stimulation of the NMDA glutamate receptor is implicated not only in the synaptic plasticity in hippocampus but may also participate in excitotoxic cell death. Using\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}-selective microssensors inserted into the diffusional field of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}in acute hippocampal slices, we describe the\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}concentration dynamics evoked by NMDA receptor activation and report profound differences along the trisynaptic loop of the hippocampus. We measured the oxygen gradient across the slice thickness and conclude that\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}measurements were performed at cell layers experiencing physiological oxygen tensions. Recordings performed at increasing distances from the point of NMDA receptor stimulation resulted in a progressive decrease of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}signals, reaching undetectable levels for distances >400 μm, supporting the notion of a wide diffusional spread of endogenously generated\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}in the hippocampus. Neither a picoinjection nor a continuous perfusion of NMDA resulted in high steady-state\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}levels; rather all signals were transient, suggesting that cells are able to efficiently respond to high\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}concentrations (typically 200-400 nM) bringing it to very low nM levels; the claimed high micromolar\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}range achieved by excessive stimulation of NMDA receptor may have to be reevaluated. The distinct responses to NMDA receptor stimulation along the trysynaptic loop suggest a differential\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}activity and/or regulation among the hippocampal subregions. These findings may be relevant for the understanding of the role of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}^{{\cdot}}{\mathrm{N}}{\mathrm{O}}\end{equation*}\end{document}in physiologic mechanisms in the hippocampus and the differential sensitivity of the hippocampal subregions to NMDA receptor-dependent neurodegeneration.