Intracellular QX-314 Inhibits Calcium Currents in Hippocampal CA1 Pyramidal Neurons. Talbot, MattHEW J. and Rod J. Sayer. Department of Physiology, University of Otago, Dunedin, New Zealand.
APStracts 3:011N, 1996.
SUMMARY AND CONCLUSIONS
1. The effects of intracellular QX-314 on Ca2+ currents were examined in CA1 pyramidal cells acutely isolated from rat hippocampus. In neurons dialysed with 10 mM QX-314 (bromide salt), the amplitude of the high-threshold Ca 2+ current was on average 20% of that in control cells and the current-voltage relationships (I-Vs) were shifted in the positive voltage direction. 2. The positive shift in the I-Vs was due to the presence of intracellular Br-, because it was reproduced by 10 mM NaBr and was not present when the chloride salt of QX-314 was used. 3. Low-threshold (T-type) Ca2+ currents, at test voltages of -50 mV and -40 mV, were on average <45% of control amplitude in cells containing 10 mM QX-314 (chloride salt) and <10% of control amplitude in cells with 10 mM QX-314 (bromide salt). 4. In neurons dialysed with 1 mM QX- 314, high-threshold Ca2+ currents were still significantly different from control and Na+ currents were not completely blocked. 5. The proportions of high-threshold Ca2+ current blocked by w -CgTx, w -Aga-IVA and nimodipine were similar in cells dialysed with 10 mM QX-314 and control cells, indicating that the drug does not selectively inhibit any of the Ca2+ channel subtypes distinguished by these antagonists.

Received  1996; accepted in final form  1996.
APS Manuscript Number J.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96