Adaptation-induced changes in sensitivity in frog olfactory receptor cells.
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.
Reisert
J
J
Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK. jr10022@hermes.cam.ac.uk
Matthews
H R
HR
D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D011896:Rana temporaria; D012903:Smell / Q000502:physiology*