Calcium Signalling in Squid Olfactory Receptor Neurons

Abstract

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.

Imaging ensemble activity in arthropod olfactory receptor neurons in situ

“…Since lobster ORNs express a typical complement of voltage-dependent conductances for neurons, including a voltage-activated calcium conductance [21], we assume the increase in Ca i we measured reflect in part the indirect activation of voltage-gated calcium channels. Calcium-induced calcium release from internal stores has also been reported from squid ORNs [22]. We assume lobster ORNs may also have internal calcium stores since bath application of ionomycin during fura-2 calibration induced a significant elevation in Ca i under extracellular Ca-free conditions [23, 24].…”

Betaine and homocysteine concentrations in foods

“…Betaine occurs at high concentrations in squid, 11−15 abalone and spinach 16 . However, onlytwo reports listed precise concentrations of Bet.…”

Role of olfaction in Octopus vulgaris reproduction

“…The anatomical descriptions of a putative olfactory organ in cephalopods first appeared in early literature (von Kölliker, 1844), followed by more recently demonstrations of their chemosensory capabilities and sensory mechanisms. To date, what is known about the olfactory organ in cephalopods comes from studies of Nautilus (Basil et al, 2000;Ruth et al, 2002) and decapods (Lucero and Gilly, 1995;Lucero et al, 1992Lucero et al, , 2000Mobley et al, 2007Mobley et al, , 2008aPiper and Lucero, 1999;Villanueva and Norman, 2008). In squid the olfactory organ is the site of a sensory epithelium resulted of ciliated supporting cells and different types of receptor cells that are bipolar neurons sending an dendritic stalk branch to the surface of the epithelium where sensory cilia are exposed to the marine environment.…”

“…Olfaction plays a role in mate choice of squid and cuttlefishes (Cummins et al, 2011;Gilly and Lucero, 1992;Lucero and Gilly, 1995;Lucero et al, 1992Lucero et al, , 2000Mobley et al, 2007;Piper and Lucero, 1999;Zatynly et al, 2000) and improves predation on crabs by cuttlefishes (Boal et al, 2000). Nautilus use olfaction for distant food odour detection and location, and perhaps for mate choice (Basil et al, 2000;Ruth et al, 2002).…”