Journal of Neuroscience, Vol 7, 3207-3214, Copyright © 1987 by Society for Neuroscience
Effects of ethanol on early potassium currents in Aplysia: cell specificity and influence of channel state
SN Treistman and A Wilson
Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
The effects of ethanol (EtOH) on the early potassium current, IA, were
examined in 3 identified neurons of Aplysia using voltage-clamp techniques.
The primary effect of EtOH on this current was a pronounced increase in the
time constant of decay. However, this effect was cell specific, being
evident in cells MCC and R15 but not in cell B1. Other parameters of IA
were not greatly affected in any of the cells, in comparison with the
effects on decay time constant. Baseline parameters of IA were measured in
each of the cells to determine whether subpopulations of IA channel might
exist, and be differentially sensitive to EtOH. While differences did
appear among cells, they were not consistent with an explanation of EtOH's
actions based upon distribution of channel subtypes. The effect of EtOH on
IA decay was dependent upon the voltage-clamp protocol used. When
inactivation of IA developed at -20 mV, the slower development of
inactivation noted above occurred. When inactivation without channel
opening was produced by means of a prepulse to -40 mV, EtOH speeded up the
development of inactivation. A number of possible explanations for these
findings are discussed. Most of the effects of EtOH occurred within 1 min
of application of the drug, suggesting relatively rapid access to the site
of action. Effects continued to develop over succeeding minutes. This
slower-developing effect may reflect either a delayed access to channels
due to slower diffusion into or lateral movement within the lipid phase of
the membrane, or it may indicate that channels are accessible to the EtOH
molecule only when in certain states.