Chem. Senses 25: 483-486,
2000
© Oxford University Press 2000
SYMPOSIUM: Adaptation in Vision and Olfaction |
Adaptation-induced Changes in Sensitivity in Frog Olfactory Receptor Cells
Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
Correspondence to be sent to: J. Reisert, Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK. e-mail: jr10022{at}hermes.cam.ac.uk
Abstract
The suction pipette technique was used to study simultaneously the odour-induced action potential and receptor current responses in frog olfactory receptor cells, which were exposed to the odour cineole for 1 s by rapidly exchanging the solution bathing their cilia. The frequency of action potential firing increased as the odour concentration was raised and saturated within a 15-fold elevation above the odour threshold, while the number of spikes fired initially grew at low-to-intermediate concentrations but then declined at higher concentrations. The receptor current response rose steadily and showed no clear sign of saturation over the 300-fold range of cineole concentration employed. The effect of adaptation on the sensitivity of olfactory receptor cells was investigated by first exposing the cell for 4 s to an adapting pre-pulse and then stimulating with a 1 s test pulse. As the pre-pulse concentration was increased, adaptation led to a progressive shift of the dose–response relationships towards higher test pulse concentrations. This resulted in a steep decline in the sensitivity of the receptor current response, combined with an even more dramatic fall in the sensitivity of the spiking responses, since the higher pre-pulse concentrations prevented the generation of action potentials at test pulse concentrations which still evoked a receptor current response.