Chemical Senses Advance Access originally published online on June 27, 2006
Chemical Senses 2006 31(7):641-647; doi:10.1093/chemse/bjl004
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Combined Behavioral and c-Fos Studies Elucidate the Vital Role of Sodium for Odor Detection
1 Faculty of Medicine, Institute of Physiology, Department of Neurophysiology, Ruhr-University Bochum, D-44780 Bochum, Germany 2 Tierphysiologie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
Correspondence to be sent to: Raimund Apfelbach, Tierphysiologie, Universität Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany. e-mail: raimund.apfelbach{at}uni-tuebingen.de
Salt, known as taste quality, is generally neglected in olfaction, although the olfactory sensory neurons stretch into the salty nasal mucus covering the olfactory epithelium (OE). Using a psychophysical approach, we directly and functionally demonstrate in the awake rat for a variety of structurally diverse odorants that sodium is a critical factor for olfactory perception and sensitivity, both very important components of mammalian communication and sexual behavior. Bathing the olfactory mucus with an iso-osmotic sodium-free buffer solution results in severe deficits in odorant detection. However, sensitivity returns fully within a few hours, indicating continuous mucus production. In the presence of sodium in the mucus covering the OE, all odorants induce odorant-specific c-Fos expression in the olfactory bulb. Yet, if sodium is absent in the mucus, no c-Fos expression is induced as demonstrated for n-octanal. Our noninvasive approach to induce anosmia in mammals here presentedwhich is fully reversible within hoursopens new possibilities to study the functions of olfactory communication in awake animals.
Key words: c-Fos expression, neural activation, n-octanal, odor detection, sodium dependency