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J. Neurophysiol. 67: 341-349 (1992)
Contribution of individual ionic currents to activity
of a model stomatogastric ganglion neuron.
Golowasch J, Buchholtz F, Epstein IR, Marder E
Department of Biology, Brandeis University, Waltham,
Massachusetts 02254-9110.
- The behavior of the mathematical model for the lateral pyloric (LP)
neuron of the crustacean stomatogastric ganglion (STG) developed in the
previous paper was further studied.
- The action of proctolin, a neuromodulatory peptide that acts directly
on the LP neuron, was modeled. The effect of the proctolin-activated current
(iproc) on the model neuron mimics the effects of proctolin
on the isolated biological LP neuron. The depolarization and increased
frequency of firing seen when iproc is activated are associated with changes
in the relative contributions of the delayed rectifier (id)
and the Ca2+-activated outward current (io(Ca)) to
the repolarization phase of the action potential.
- The effects of turning off the A-current (iA) in the model
were compared with those obtained by pharmacologically blocking iA
in the biological neuron. iA appears to regulate action-potential
frequency as well as postinhibitory rebound activity.
- The role of iA on the rhythmic activity of the cell was
studied by modifying several of its parameters while periodically activating
a simulated synaptically activated conductance, isyn.
- The effects of manipulations of the maximal conductances (g) for id
and io(Ca) were studied. id strongly influences action-potential
frequency, whereas io(Ca) strongly influences action-potential
duration.
- Modifications of the maximal conductance of the inward Ca2+
current (iCa) were compared with the effects of blocking iCa
in the real cell.
- The role of the hyperpolarization-activated inward current (ih)
during ongoing rhythmic activity was assessed by periodically activating
isyn while modifying ih.
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