Multiple conductances cooperatively regulate spontaneous bursting in mouse olfactory bulb external tufted cells

Area of Science:

• Neuroscience
• Computational Neuroscience
• Olfactory System Physiology

Background:

• External tufted (ET) cells are juxtaglomerular neurons in the olfactory bulb.
• ET cells exhibit spontaneous action potential bursting, even without synaptic input.
• The intrinsic ionic mechanisms underlying ET cell autonomous bursting remain largely unknown.

Purpose of the Study:

• To elucidate the intrinsic voltage-dependent conductances responsible for autonomous bursting in ET cells.
• To identify the specific ion channels and currents involved in initiating, sustaining, and terminating these bursts.
• To understand how these intrinsic properties shape olfactory glomerular circuit output.

Main Methods:

• Electrophysiological recordings in ET cells.
• Pharmacological manipulation of specific ion channels (e.g., L-type Ca2+, BK channels).
• Modeling of ionic conductances to understand their cooperative roles.

Main Results:

• Identified four key conductances: hyperpolarization-activated inward current (Ih), persistent Na+ current (INaP), low-voltage-activated calcium current (IL/T), and large-conductance Ca2+-dependent K+ current (IBK).
• Demonstrated Ih sets membrane potential, INaP and IL/T generate the depolarizing envelope, and IBK terminates bursts.
• Novel findings include the role of L-type Ca2+ channels in bursting and IBK channels in regulating burst duration.

Conclusions:

• Autonomous bursting in ET cells is a cooperative process regulated by a specific set of voltage-dependent ion channels.
• The interplay between L-type Ca2+ channels and BK channels is crucial for burst dynamics.
• Modulation of these conductances can significantly influence olfactory bulb circuit processing and output to higher brain centers.