QUANTAL-LIKE CURRENT FLUCTUATIONS INDUCED BY ODORANTS IN OLFACTORY RECEPTOR-CELLS

MANY sensory systems have evolved signal detection capabilities that a re limited only by the physical attributes of the stimulus(1). For exa mple, 'hair' cells of the inner ear can detect displacements of atomic dimensions(2). Likewise, both in vertebrates and in invertebrates pho toreceptors can detect a single photon(3,4). The olfactory stimulus al so has a quantal unit, the single odorant molecule, Insects are report edly able to detect a single pheromone molecule(5), whereas quantal re sponses in vertebrate olfactory receptor cells have not been reported yet. Psychophysical measurements indicate that a minimum of 50 odorant molecules are necessary for human olfactory detection, suggesting tha t an individual receptor may be activated ba a single odorant molecule (6). We report here measurements of current fluctuations induced by od orants that suggest a quantal event of about 03-1 pA, presumably trigg ered by the binding of a single odorant molecule.