Calcium Signalling in Squid Olfactory Receptor Neurons

Isolated squid olfactory receptor neurons respond to dopamine and betaine with hyperpolarizing conductances. We used Ca2+ imaging techniques to determine if changes in intracellular Ca2+ were involved in transducing the hyperpolarizing odor responses. We found that dopamine activated release of Ca2+ from intracellular stores while betaine did not change internal Ca2+ concentrations. Application of 10 mM caffeine also released Ca2+ from intracellular stores, suggesting the presence of ryanodine-like receptors. Depletion of intracellular stores with 100 µM thapsigargin revealed the presence of a Ca2+ store depletion-activated Ca2+ influx. The influx of Ca2+ through the store-operated channel was reversibly blocked by 10 mM Cd2+. Taken together, these data suggest a novel odor transduction system in squid olfactory receptor neurons involving Ca2+ release from intracellular stores.