Immunohistochemical evidence for the Na+/Ca2+ exchanger in squid olfactory neurons

The olfactory organs fron the squid Lolliguncula brevis are composed of a pseudostratifies epithelium containing five morphological subtypes of chemosensory neurons and ciliated support cells. Physiological recordings have been made from two of the subtypes and only the type 4 neuron has been studied in detail. Odour-stimulating increases in intracellular calcium and rapid activation of an electrogenic Na+/Ca2+ exchanger current in type 4 neurons suggest that the exchanger proteins are localized very close to the transduction machinery. Electrophysiological studies have shown that olfactory signal transduction takes place in the apical ciliary regions of olfactory neurons. Using polyclonal antiserum against squid Na+/Ca2+ proteins , we observed specific staining in the ciliary region of cells that resemble type 2, 3, 4 and 5 neurons, Staining was also observed in axon bundles, and in muscle tissue. Collectively, these data support the model that Na+/Ca2+ exchanger proteins are localized to transduction during chemosensory responses.