Immunohistochemical evidence for the Na+/Ca2+ exchanger in squid olfactoryneurons

The olfactory organs fron the squid Lolliguncula brevis are composed of a p seudostratifies epithelium containing five morphological subtypes of chemos ensory neurons and ciliated support cells. Physiological recordings have be en made from two of the subtypes and only the type 4 neuron has been studie d 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 transd uction machinery. Electrophysiological studies have shown that olfactory si gnal transduction takes place in the apical ciliary regions of olfactory ne urons. Using polyclonal antiserum against squid Na+/Ca2+ proteins , we obse rved 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 mus cle tissue. Collectively, these data support the model that Na+/Ca2+ exchan ger proteins are localized to transduction during chemosensory responses.