Effect of the glial envelope on extracellular K(+) diffusion in olfactory glomeruli

Area of Science:

• Neuroscience
• Olfactory System Biology
• Computational Neuroscience

Background:

• Olfactory neuropils in many species feature spherical glomeruli surrounded by glial borders.
• The functional impact of this glomerular organization on olfactory information processing remains unclear.
• Odor stimulation causes potassium ion ([K+]) accumulation around activated olfactory receptor axons within glomeruli.

Purpose of the Study:

• To investigate the time course and magnitude of potassium accumulation in olfactory glomeruli.
• To explore the potential effects of this potassium accumulation on neural activity.
• To model potassium diffusion within and between glomeruli in the moth Manduca sexta.

Main Methods:

• Development of a theoretical model simulating potassium diffusion in glomerular extracellular spaces.
• Utilizing spherical coordinates and a finite-difference method to solve time-dependent diffusion equations.
• Assumption that activated axons release potassium, which then diffuses through extracellular spaces and glial borders.

Main Results:

• Glial envelopes act as significant barriers, restricting potassium spread between adjacent glomeruli.
• This barrier effect reduces the probability of glomeruli cross-talk.
• Elevated extracellular potassium levels within activated glomeruli persist for seconds, influencing neural activity.

Conclusions:

• Glial borders play a crucial role in maintaining glomerular-specific signaling.
• The observed potassium dynamics may enhance olfactory sensitivity and discrimination.
• The model provides insights into the functional significance of glomerular organization in olfaction.