Experience-dependent maturation of the glomerular microcircuit.

Area of Science:

• Neuroscience
• Developmental Biology
• Cellular Electrophysiology

Background:

• Neural circuit development is shaped by both chemical and electrical transmission.
• Electrical transmission via gap junctions plays a role in synchronized brain activity, notably in the olfactory bulb.
• Gap junctions between mitral cells synchronize firing within olfactory bulb glomeruli.

Purpose of the Study:

• To investigate the roles of sensory experience and connexin 36 (Cx36)-mediated gap junctions in the development of the olfactory bulb microcircuit.
• To understand the transition from electrical to chemical transmission in mitral cells.

Main Methods:

• Electrophysiological recordings in mice.
• Manipulating sensory experience through unilateral naris occlusion.
• Assessing morphological development and membrane conductance changes.
• Investigating mitral-mitral excitatory postsynaptic currents (EPSCs) in wild-type and Cx36 knockout mice.

Main Results:

• Coupling coefficients were high in young mice but decreased after postnatal day 10 due to increased membrane conductance.
• Sensory deprivation arrested developmental changes in mitral cell morphology, membrane conductance, and coupling.
• A glutamate-mediated mitral-mitral EPSC emerged by postnatal day 30 in normal mice but was absent in Cx36 knockout mice.

Conclusions:

• Olfactory bulb microcircuit development requires both sensory experience and Cx36 gap junctions.
• An experience-dependent transition from electrical to combined electrical and chemical transmission occurs.
• This transition may fine-tune the response properties of the glomerular microcircuit.