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R Dörner

Publications and source records attributed to R Dörner.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effects of glutamatergic agonists and antagonists on membrane potential and intracellular Na+ activity of leech glial and nerve cells.

The membrane potential of neuropile glial cells and Retzius neurones in the central nervous system of the leech Hirudo medicinalis was measured using electrolyte-filled single-barreled microelectrodes. Intracellular Na+ activity (aNai) was recorded with Na(+)-sensitive double-barreled microelectrodes. Bath-application of kainate, quisqualate and L-glutamate elicited concentration-dependent membrane depolarizations in both cell types as demonstrated by dose-response curves. The competitive quinoxalinedione antagonists 6,7-dinitroquinoxaline-2,3-dione (DNQX) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the non-NMDA glutamate receptor inhibited the membrane depolarizations in neuropile glial cells completely, but in Retzius neurones only partially. These results confirm that leech neuropile glial cells have a kainate- and quisqualate-preferring non-NMDA glutamate receptor similar to that in the Retzius neurones. The initial decrease in aNai in neuropile glial cells in kainate- or quisqualate-containing solutions and the afterhyperpolarization in these glial cells and the Retzius neurones following the removal of both glutamate antagonists, were blocked in the presence of the cardiac glycoside ouabain (10(-4) M). In saline solutions containing 42.5 mM Li+ instead of Na+ the afterhyperpolarizations were blocked in neuropile glial cells and Retzius neurones. We conclude that the initial aNai changes and the afterhyperpolarization could be due to the stimulation of the electrogenic Na+/K+ pump in the glial and neuronal membranes.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

The regulation of pH in the central nervous system.

The pHi regulation from intracellular acidosis in the central nervous system appears to be mediated by mechanisms driven by the large inwardly directed Na+ gradient. The involvement of these mechanisms in pHi regulation of neurones and glial cells has been investigated in the leech central nervous system using ion-selective microelectrodes. For recovery from acidification, there appear to be three separate mechanisms: Na+/H+ exchange, Na(+)-dependent Cl-/HCO3- exchange, and Na+-HCO3- cotransport. All three mechanisms have a profound effect on the maintenance of pHi homeostasis in glial cells; whereas in leech neurones, as in other neuronal cells studied previously, the predominant mechanisms are Na+/H+ and Na(+)-dependent Cl-/HCO3- exchange. In addition to acid extrusion mechanisms we also found evidence for Na(+)-independent Cl-/HCO3- exchange. At alkaline pHi this exchanger may mediate some of the pHi recovery from intracellular alkalinization.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗