F. Zufall et al., RAPID APPLICATION AND REMOVAL OF 2ND MESSENGERS TO CYCLIC NUCLEOTIDE-GATED CHANNELS FROM OLFACTORY EPITHELIUM, Proceedings of the National Academy of Sciences of the United Statesof America, 90(20), 1993, pp. 9335-9339
The last step in the second-messenger cascade mediating vertebrate olf
actory transduction is the direct opening of a nonspecific cation chan
nel by cAMP. The kinetic properties of this interaction are critical i
n determining the time course of the sensory response. To analyze thes
e properties, excised inside-out membrane patches containing either th
e native channel from salamander olfactory-receptor neurons or a recom
binant rat olfactory cyclic nucleotide-gated channel were exposed to s
hort pulses of known concentrations of cAMP or cGMP to mimic a rapid a
nd transient production of second messenger. Channel activity outlaste
d cyclic nucleotide pulses for several hundred milliseconds. This effe
ct was due to an intrinsic property of the olfactory channel protein b
ecause it did not occur with cGMP-activated channels from retinal phot
oreceptors. Gating kinetics of the olfactory channel were both voltage
and agonist dependent. These results demonstrate that the overall slo
w channel-gating kinetics could account for the difference in time cou
rse between the odor-induced changes in cAMP concentration and the sub
sequent sensory generator current.