Aa. Selyanko et Da. Brown, REGULATION OF M-TYPE POTASSIUM CHANNELS IN MAMMALIAN SYMPATHETIC NEURONS - ACTION OF INTRACELLULAR CALCIUM ON SINGLE-CHANNEL CURRENTS, Neuropharmacology, 35(7), 1996, pp. 933-947
Currents through single M-type potassium channels were recorded in mem
brane patches excised from rat superior cervical sympathetic neurons.
Application of Ca2+ to the internal face of inside-out patches produce
two forms of M-channel inhibition: a slow, all-or-nothing suppression
of activity; and a fast block associated with a concentration-depende
nt shortening of open times compatible with open-channel block. Both f
orms of block were enhanced by patch depolarization. Neither was repli
cated or affected by Mg2+, and both could be recorded in the absence o
f intracellular ATP, implying that they did not involve phosphorylatio
n. Since the block was reversible in the absence of ATP and since alka
line phosphatase did not reduce channel activity, block was unlikely t
o have resulted from dephosphorylation. In cell-attached patch recordi
ngs, M-channel activity increased during exposure of the cell to Ca2+-
free solution and was rapidly reduced on applying 2 mM Ca2+ to the ext
ra-patch solution. This suggests that M-channel activity in these neur
ons may be tonically regulated by variations in resting intracellular
[Ca2+]. Copyright (C) 1996 Elsevier Science Ltd