Phase-resetting curve determines how BK currents affect neuronal firing.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Ion Channel Physiology

Background:

• Large conductance calcium- and voltage-gated potassium (BK) channels play critical roles in neuronal excitability.
• Experimental studies show paradoxical effects of BK channel blockers on neuronal firing rates, with increases or decreases observed depending on neural subtype and brain region.
• The underlying mechanisms for these varied effects remain poorly understood.

Purpose of the Study:

• To elucidate the mechanisms by which BK channel activity influences neuronal firing rates.
• To predict when BK channel modulation will increase or decrease firing rates using theoretical modeling.
• To explain the apparently contradictory experimental findings regarding BK channel antagonists.

Main Methods:

• Utilized phase-resetting curve (PRC) theory to analyze the impact of BK currents on neural models.
• Investigated the influence of BK currents in neural models with different PRC types (positive-only vs. type II with negative regions).
• Examined the effects of BK currents in the presence of other conductances (e.g., I(m), I(h)) and varying depolarizing input amplitudes.

Main Results:

• The addition of BK currents consistently decreased firing rate in models with positive-only PRCs.
• In models with type II PRCs (possessing a negative region), BK currents were shown to increase firing rate.
• The interplay between BK channels, other conductances, and input drive modulates firing rate responses.

Conclusions:

• Phase-resetting curve theory provides a formal framework to explain the dual effects of BK channels on neuronal firing rates.
• The shape of the PRC is a critical determinant of whether BK channel activity increases or decreases firing rate.
• This work offers a mechanistic explanation for the context-dependent effects of BK channel modulation observed in experimental studies.