Homeostasis of Mitochondrial Ca Stores Is Critical for Signal Amplification in Olfactory Sensory Neurons

Insects detect volatile chemosignals with olfactory sensory neurons (OSNs) that express olfactory receptors. Among them, the most sensitive receptors are the odorant receptors (ORs), which form cation channels passing Ca. OSNs expressing different groups of ORs show varying optimal odor concentration ranges according to environmental needs. Certain types of OSNs, usually attuned to high odor concentrations, allow for the detection of even low signals through the process of sensitization. By increasing the sensitivity of OSNs upon repetitive subthreshold odor stimulation, can detect even faint and turbulent odor traces during flight. While the influx of extracellular Ca has been previously shown to be a cue for sensitization, our study investigates the importance of intracellular Ca management. Using an open antenna preparation that allows observation and pharmacological manipulation of OSNs, we performed Ca imaging to determine the role of Ca storage in mitochondria. By disturbing the mitochondrial resting potential and induction of the mitochondrial permeability transition pore (mPTP), we show that effective storage of Ca in the mitochondria is vital for sensitization to occur, and release of Ca from the mitochondria to the cytoplasm promptly abolishes sensitization. Our study shows the importance of cellular Ca management for sensitization in an effort to better understand the underlying mechanics of OSN modulation.