Calcium signalling and regulation in olfactory neurons.

Area of Science:

• Neuroscience
• Olfactory receptor neuron physiology
• Cellular signaling

Background:

• Olfactory sensory neurons (OSNs) detect odors via cilia.
• Odorant detection involves intracellular calcium ion (Ca2+) dynamics.
• Ca2+ signaling is crucial for both neuronal excitation and adaptation.

Purpose of the Study:

• To elucidate the specific roles of Ca2+ in vertebrate olfactory sensory neurons.
• To characterize the mechanisms of Ca2+ mediated excitation and adaptation.
• To understand the regulation of intracellular Ca2+ levels in olfactory cilia.

Main Methods:

• Direct visualization of intracellular Ca2+ increase in cilia.
• Analysis of Ca2+ entry through cyclic adenosine monophosphate (cAMP)-gated channels.
• Investigation of Ca2+ interactions with chloride channels and calmodulin.
• Study of the Na+/Ca2+ exchanger's role in Ca2+ extrusion.

Main Results:

• Odorant stimulation leads to a Ca2+ increase in cilia via cAMP-gated channels.
• Ca2+ directly activates ciliary chloride channels, causing Cl- efflux and neuronal depolarization.
• Ca2+ and calmodulin mediate odorant adaptation by desensitizing cAMP-gated channels.
• A Na+/Ca2+ exchanger restores basal Ca2+ levels by extruding Ca2+ from cilia.

Conclusions:

• Ca2+ plays a dual role in olfactory neurons: excitation and adaptation.
• Ca2+ activation of Cl- channels provides high-gain, low-noise amplification.
• Ca2+ and calmodulin-mediated desensitization is key to olfactory adaptation.
• The Na+/Ca2+ exchanger is essential for resetting Ca2+ levels after stimulation.