Genesis of bursting activity: Role of inhibitory constraints on persistent Na+ currents

Abstract

Some neurons express a plateau of spike activity greatly outlasting a stimulus, whereas others do not. This difference could be due to differential expression of ion channels (e.g., persistent Na+, and Ca2+) or similar expression of channels that differ in their properties. We compared three Aplysia neurons with varying capacity to generate plateau potentials: B51 with self-terminating plateaus, B64 with plateau potentials that do not self-terminate, and the regular spiking neuron B8. Our results indicate the three neurons expressed outward currents IA and ID, voltage-gated Ca2+ currents ICaL and ICaR, and persistent inward INaP. The most notable difference observed was a larger IA, ID, and IKCa currents in B8, and the plateau generating B64 did not express IKCa. Computational models suggest outward currents suppress and temporally constrain the plateau potential and that inward Ca2+ currents suppress plateau potentials when coupled with IKCa.