AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 6 1816-R1823, Copyright © 1994 by American Physiological Society
Temperature increase abolishes ability of turtle olfactory receptors to discriminate similar odorant
T. Hanada, M. Kashiwayanagi and K. Kurihara
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
We examined the effects of temperature changes on odor-discriminating
ability of turtle olfactory receptors in vivo by applying the
cross-adaptation method to the olfactory bulbar responses. The olfactory
system discriminated well all eight pairs of odorants examined at 5 and 18
degrees C. The ability of the olfactory receptors to discriminate pairs of
odorants having similar structures (e.g., trans-3-hexenol and
cis-3-hexenol; d-carvone and l-carvone) was reversibly abolished by
increasing the temperature up to 40 degrees C, whereas discrimination of
odorants having quite different structures was much less affected. The
membrane fluidity of cells isolated from turtle olfactory epithelia and
liposomes made of lipids extracted from the epithelia changed in a similar
temperature range as for the decrease of the odor-discriminating ability,
suggesting that an increase in membrane fluidity is correlated with the
abolishment of the odor-discriminating ability. The present results also
suggest that in vivo desensitization (adaptation) occurs not at the
cellular level but at the receptor level. This mechanism was supported by
the data recorded from a single olfactory cilium, showing that a single
cell has both receptors for l-carvone and d-carvone and that the response
to d-carvone appeared after the response to l-carvone was adapted.
