THE RELATION BETWEEN STIMULUS AND RESPONSE IN OLFACTORY RECEPTOR-CELLS OF THE TIGER SALAMANDER

1. Olfactory receptor cells were isolated from the adult tiger salamander Ambystoma tigrinum and the current in response to odorant stimuli was measured with the whole-cell voltage-clamp technique while odorants at known concentrations were rapidly applied for controlled exposure times. 2. Three odorants, cineole, isoamyl acetate and acetophenone, were first applied at 5 x 10(-4) m. Out of forty-nine cells tested, 53 % responded to one odorant only, 22 % to two odorants and 25 % to all three odorants. 3. The amplitude of the current in response to a given odorant concentration was found to be dependent on the duration of the odorant stimulus and reached a saturating peak value at 1.2 s of stimulus duration. 4. The current measured at the peak of the response for odorant steps of 1.2 s as a function of odorant concentration was well described by the Hill equation for the three odorants with Hill coefficients higher than 1 and K 1/2 (odorant concentration needed to activate half the maximal current) ranging from 3 x 10(-6) to 9 x 10(-5) m. 5. It is concluded that olfactory receptor cells are broadly tuned and have a low apparent affinity for odorants, integrate stimulus information over time, and have a narrow dynamic range.