Olfactory neurons exhibit heterogeneity in depolarization-induced calcium changes

Area of Science:

• Neuroscience
• Cell Biology
• Sensory Systems

Background:

• Olfactory neurons are crucial for detecting environmental cues.
• Understanding intracellular calcium dynamics is key to olfactory signaling.
• Channel catfish (Ictalurus punctatus) provide a model for fish olfaction research.

Purpose of the Study:

• To characterize intracellular calcium responses in isolated channel catfish olfactory neurons.
• To identify the role of L-type calcium channels in olfactory neuron depolarization.
• To investigate the functional heterogeneity of olfactory neurons.

Main Methods:

• Isolation of olfactory neurons using papain treatment.
• Intracellular calcium measurement using fura-2 acetoxymethyl ester (fura-2/AM).
• Electrophysiological recordings of unitary calcium currents and pharmacological inhibition with nimodipine.

Main Results:

• Isolated olfactory neurons exhibit a wide range of intracellular calcium levels.
• Potassium-induced depolarization increases intracellular calcium in 21% of cells via extracellular calcium influx.
• Nimodipine inhibits calcium increase and blocks L-type calcium currents, confirming their involvement.
• Olfactory neurons display heterogeneous responses to depolarization, categorized into rapid, slow, and non-responsive groups.

Conclusions:

• Channel catfish olfactory neurons possess functionally distinct subpopulations based on their calcium signaling response.
• L-type calcium channels play a significant role in mediating calcium influx upon depolarization in a subset of olfactory neurons.
• This heterogeneity suggests specialized roles for different olfactory neuron types in signal processing.