Kinetics and subunit composition of NMDA receptors in respiratory-related neurons

Authors

  • I. Paarmann,

    1. Glutamate Receptor Laboratory, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
    2. Department of Neurochemistry, Max-Planck-Institute for Brain Research, Frankfurt, Germany
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  • D. Frermann,

    1. Center for Physiology and Pathophysiology, University of Göttingen, Göttingen, Germany
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  • B. U. Keller,

    1. Center for Physiology and Pathophysiology, University of Göttingen, Göttingen, Germany
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  • C. Villmann,

    1. Institute for Biochemistry, University of Erlangen-Nuremberg, Erlangen, Germany
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  • H. G. Breitinger,

    1. Institute for Biochemistry, University of Erlangen-Nuremberg, Erlangen, Germany
    2. Biochemistry Department, The German University in Cairo, Al Tagamoa Al Khames, New Cairo City, Egypt
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  • M. Hollmann

    1. Glutamate Receptor Laboratory, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
    2. Department of Biochemistry I – Receptor Biochemistry, University of Bochum, Bochum, Germany
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Address correspondence and reprint requests to Professor Dr Michael Hollmann, Biochemistry I – Receptor Biochemistry, University of Bochum, Building NC, Level 6, Room 170, Universitätsstr. 150, D-44780 Bochum, Germany. E-mail: Michael.Hollmann@ruhr-uni-bochum.de

Abstract

NMDA receptors are involved in a variety of brainstem functions. The excitatory postsynaptic NMDA currents of pre-Bötzinger complex interneurons and hypoglossal motoneurons, which are located in the medulla oblongata, show remarkably fast deactivation kinetics of approximately 30 ms compared with NMDA receptors in other types of neurons. Because structural heterogeneity might be the basis for physiological properties, we examined the expression of six NMDA receptor subunits (NMDAR1, NR2A−2D, and NR3A) plus eight NMDR1 splice variants in pre-Bötzinger complex, hypoglossal and, for comparison, neurons from the nucleus of the solitary tract in young rats using single cell multiplex RT–PCR. Expression of NR2A, NR2B, and NR2D was observed in all three cell types while NR3A was much more abundant in pre-Bötzinger complex interneurons, which belong to the rhythm generator of respiratory activity. In hypoglossal neurons, the NMDAR1 splice variants NMDAR1–4a and NMDAR1–4b were found. In neurons of the nucleus of the solitary tract, instead of NMDAR1–4b, the NMDAR1–2a splice variant was detected. This differential expression of modulatory splice variants might be the molecular basis for the characteristic functional properties of NMDA receptors, as neurons expressing a special NMDAR1 splice variant at the mRNA level show fast kinetics compared with neurons lacking this splice variant.

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