A model of slow plateau-like oscillations based upon the fast Na+ current in a window mode

Divalent ions, which block Ca2+ currents, combined with partial block of ou tward currents give rise to slow plateau-like oscillations (10-50 s period) with long duration plateaus and long inter-plateau intervals in leech hear t interneurons (Opdyke, Calabrese, J. Comp. Physiol. 175 (1994) 781-789.) W e present a simplified mathematical model that replicates the main characte ristics of these observations and suggests an underlying biophysical mechan ism. A model containing transient Na+ current (I-Na), leakage and outward c urrents can generate oscillations with long plateau duration. The plateaus arise from a window mode of I-Na and do not require noninactivating Na+ cur rent (I-Na). The long inter-plateau intervals are produced reliably after i ncluding I-p. (C) 2001 Elsevier Science B.V. All rights reserved.