A calcium-activated cation nonselective current contributes to the fast
afterdepolarization in rat prefrontal cortex neurons
Samir Haj-Dahmane and Rodrigo Andrade
Dept. of Psychiatry and Behavioral Neurosciences and Cellular and Clinical
Neurobiology Training Program Wayne State University School of Medicine
540 E Canfield St. Detroit, MI 48201 USA
APStracts 4:0093N, 1997.
ABSTRACT
Pyramidal cells of layer V in rat prefrontal cortex display a prominent fast
afterdepolarization following an action potential. This afterdepolarization is
blocked by replacing extracellular calcium with magnesium, by the application
of the calcium-channel blocker cadmium and by buffering intracellular calcium
at near physiological levels. Thus this fast ADP appears mediated by a
calcium-activated current.
A prominent afterdepolarization is also observed following a calcium spike
recorded in the presence of TTX. The current underlying this
afterdepolarization was recorded using a hybrid current-voltage protocol. A
strong afterdepolarization could be observed in the presence of potassium
channel blockers as well as at ECl. Furthermore, the current underlying the
ADP increased with hyperpolarization in the subthreshold range and displayed
an extrapolated reversal potential near +30 mV. Reducing the ratio of
extracellular to intracellular sodium inhibited the current underlying the
afterdepolarization and caused a hyperpolarizing shift in its reversal
potential. We conclude that these cells express a calcium activated cation
nonselective current whose activation contributes to the generation of the
fast afterdepolarization. This current could play an important role in
determining the firing properties of pyramidal cells in cortex.
Received 11 Janaury 1997; accepted in final form 5 June 1997.
APS Manuscript Number J023-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 July 1997