Two types of BK channels in immature rat neocortical pyramidal neurons . Kang, Jian, John R. Huguenard and David A. Prince. Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305 .
APStracts 3:0197N, 1996.
The properties of large conductance Ca 2+ -activated K + channels (BK channels) were investigated in neocortical infragranular pyramidal neurons using inside-out patch recordings. Neurons were acutely isolated from slices of newborn to 28 day old rats (P0- P28) by using minimal protease exposure followed by trituration with a vibrating glass probe. Two types of BK channels, slow-gating and fast-gating, were observed in immature neurons (P0- P5), while only slow-gating BK were found in more mature neurons. Fast-gating BK channels differed in conductance, voltage-dependence and kinetics from the slow-gating ones. The properties of fast-gating channels included a conductance of 145 +/- 12.9 pS; frequent openings with short mean open times that were relatively voltage-independent, mean closed times that showed a voltage-dependent increase, a voltage-dependent decrease in open probability (P o ). The properties of slow-gating channels contrasted with those of the fast-gating ones, in that the former had a conductance of 181 +/- 3.9 pS, longer mean open times that showed a voltage-dependent increase, mean closed times that showed a marked voltage-dependent decrease, a voltage-dependent increase in P o , and slight inward rectification. The significance of these developmental variations in channel properties is discussed.

Received 28 May 1996; accepted in final form 13 September 1996.
APS Manuscript Number J420-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996