Odorant-regulated Ca2+ gradients in rat olfactory neurons.
Olfactory neurons respond to odors with a change in conductance that mediates an influx of cations including Ca2+. The concomitant increase in [Cai] has been postulated to play a role in the adaptation to maintained odorant stimulation (Kurahashi, T., and T. Shibuya. 1990. Brain Research. 515:261-268. Kramer, R. H., and S. A. Siegelbaum. 1992. Neuron. 9:897-906. Zufall, F., G. M. Shepherd, and S. Firestein. 1991. Proceedings of the Royal Society of London, B. 246:225-230.) We have imaged the distribution of [Cai] in rat olfactory neurons (RON) using the Ca2+ indicator fura-2. A large percentage of the RON (42%, n = 35) responded to odorants with an increase in [Cai]. About half of the responding neurons displayed an increase in [Cai] at the apical end of the cell, but not at the soma. Moreover, in those cells that responded to odors with a standing [Cai] gradient, the gradient could be maintained for long periods of time (minutes) provided that the cells were continuously stimulated. In contrast, K(+)-induced depolarization elicited a more homogeneous increase in [Cai]. The spatially inhomogeneous increase in [Cai] elicited by odorants in some cells has important implications for the role of Ca2+ in adaptation because channels and enzymes regulated by Ca2+ will be affected differently depending on their location.
Restrepo
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Monell Chemical Senses Center, Philadelphia, Pennsylvania 19104.
Okada
Y
Y
Teeter
J H
JH
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002118:Calcium / Q000032:analysis* / Q000493:pharmacokinetics / Q000494:pharmacology; D015220:Calcium Channels / Q000032:analysis / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D016257:Fura-2; D009475:Neurons, Afferent / Q000737:chemistry / Q000502:physiology; D009812:Odorants; D009832:Olfactory Nerve / Q000737:chemistry* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018035:Receptors, Odorant / Q000032:analysis / Q000502:physiology
D015220:Calcium Channels; D018035:Receptors, Odorant; D005576:Colforsin; D002118:Calcium; D016257:Fura-2