J. Golowasch et al., Activity-dependent regulation of potassium currents in an identified neuron of the stomatogastric ganglion of the crab Cancer borealis, J NEUROSC, 19(20), 1999, pp. A1-A5
Identified neurons of the stomatogastric ganglion of the crab Cancer boreal
is were voltage-clamped, and the current densities of three K+ currents wer
e measured. The current densities of each of the three K+ currents varied t
wofold to fivefold in inferior cardiac (IC) neurons from different animals.
Conventionally, this degree of variability has been attributed to experime
ntal artifacts. Instead, we suggest that it reflects a natural variability
that may be related to an underlying process of plasticity. First, we found
that there is no fixed ratio among the three K+ currents. Second, we found
that several hours of stimulation with depolarizing current pulses (0.5 se
c duration at 1 Hz) altered the current density of the Ca2+-dependent outwa
rd current, I-K(Ca), and the transient outward current, I-A. This stimulati
on paradigm mimics the normal pattern of activity for these neurons. The ef
fect of stimulation on the I-A current density was eliminated when Ca2+ inf
lux was blocked by extracellular Cd2+. In contrast, the K+ current densitie
s of the lateral pyloric (LP) neuron were unaffected by the same pattern of
stimulation, and the currents expressed by both the IC and the LP neurons
were insensitive to hyperpolarizing pulses at the same frequency. We conclu
de that the conductance densities expressed by neurons may vary continually
depending on the recent history of electrical activity in the preparation,
and that intracellular Ca2+ may play a role in the processes by which acti
vity influences the regulation of current densities in neurons.