Ca2+- and Metabolism-Related Changes Of Mitochondrial Potential In Voltage-Clamped CA1 Pyramidal Neurons In Situ. S. Schuchmann2, M. Lückermann1, A. Kulik1, U. Heinemann2 and K. Ballanyi1. 1II. Physiologisches Institut, Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany and 2Institut für Physiologie, Humboldt-Universität Berlin, Universitätsklinikum Charité, Tucholskystr. 2, D-10117 Berlin, Germany.
APStracts 6:0540N, 1999.
In hippocampal slices from rats, dialysis with rhodamine-123 (Rh-123) and/or fura-2 via the patch electrode allowed monitoring of mitochondrial potential (?() changes and intracellular Ca2+ ([Ca2+]i) of CA1 pyramidal neurons. Plasmalemmal depolarisation to 0 mV caused a mean [Ca2+]i rise of 300 nM and increased Rh-123 fluorescence signal (RFS) by up to 50 % of control. The evoked RFS, indicating depolarisation of ?(, and the [Ca2+]i transient were abolished by Ca2+-free superfusate or exposure of Ni2+/Cd2+. Simultaneous measurements of RFS and [Ca2+]i showed that the kinetics of both the Ca2+ rise and recovery were considerably faster than those of the ?( depolarisation. The plasmalemmal Ca2+/H+ pump blocker eosin-B potentiated the peak of the depolarisation-induced RFS and delayed recovery of both the RFS and [Ca2+]i transient. Thus the ?( depolarisation due to plasmalemmal depolarisation is related to mitochondrial Ca2+ sequestration secondary to Ca2+ influx through voltage-gated Ca2+ channels. CN- elevated [Ca2+]i by <50 nM but increased RFS by 221 % as a result of extensive depolarisation of ?(. Oligomycin decreased RFS by 52 % without affecting [Ca2+]i. In the presence of oligomycin, CN- and FCCP elevated [Ca2+]i by <50 nM and increased RFS by 285 and 290 %, respectively. Accordingly, the metabolism-related ?( changes are independent of [Ca2+]i. Imaging techniques revealed that evoked [Ca2+]i rises are distributed uniformly over the soma and primary dendrites, whereas corresponding changes in RFS occur more localised in subregions within the soma. The results show that microfluorometric measurement of the relation between mitochondrial function and intracellular Ca2+ is feasible in whole-cell recorded mammalian neurons in situ.
Received 3 June 1999; accepted in final form 22 October 1999.
APS Manuscript Number J445-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999