Journal of Neuroscience, Vol 12, 989-1000, Copyright © 1992 by Society for Neuroscience
Three types of early transient potassium currents in Aplysia neurons
Y Furukawa, ER Kandel and P Pfaffinger
Howard Hughes Medical Institute, College of Physicians and Surgeons of Columbia University, New York, New York 10032.
In an attempt to categorize the various early transient K+ currents (A-
type K+ currents) present in mature neurons, we have explored these
currents in the identified neurons in the abdominal ganglion of the
mollusk, Aplysia californica. Three distinct types of A-type K+ currents
(IAfast, IAslow, and IAdepol) were found. The activation and the
steady-state inactivation properties of two of these currents, IAfast and
IAslow, were similar to conventional A-type K+ currents. By contrast, those
of the third current, IAdepol, were shifted to more depolarized potentials.
Whereas the decay time constants of IAfast were voltage dependent, those of
IAslow and IAdepol were almost voltage independent. The recovery from
inactivation of IAfast and IAslow was much faster than that of IAdepol. In
addition, IAdepol was more sensitive to 4-aminopyridine (4-AP) than other
currents and was almost completely blocked by 1 mM 4-AP. All the currents
were depressed by forskolin or 1,9-dideoxyforskolin, but not by cAMP
analogs. None of these currents were blocked by external tetraethylammonium
(50 mM). These results indicate that there are at least three subtypes of
A-type K+ currents in the Aplysia CNS. Of these, two currents, IAfast and
IAslow, are conventional A-type K+ currents, whereas the third current,
IAdepol, is a novel early transient K+ current.
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