citralva and geraniol

Olfactory chemotransduction involves a signaling cascade. In addition to triggering transduction, odors suppress ion conductances. By stimulating with brief odorant pulses, we observed a current associated with odor-induced suppression of voltage-gated conductances and studied its time dependence. We characterized this suppression current in isolated Caudiverbera caudiverbera olfactory neurons. All four voltage-gated currents are suppressed by odor pulses in almost every neuron, and suppression is caused by odors inducing excitation and by those inducing inhibition, indicating a nonselective phenomenon, in contrast to transduction. Suppression has a 10-fold shorter latency than transduction. Suppression was more pronounced when odors were applied to the soma than to the cilia, opposite to transduction. Suppression was also present in rat olfactory neurons. Furthermore, we could induce it in Drosophila photoreceptor cells, demonstrating its independence from the chemotransduction cascade. We show that odor concentrations causing suppression are similar to those triggering chemotransduction and that both suppression and transduction contribute to the odor response in isolated olfactory neurons. Furthermore, suppression affects spiking, implying a possible physiological role in olfaction.

Topics: Action Potentials; Acyclic Monoterpenes; Aldehydes; Animals; Anura; Cilia; Dose-Response Relationship, Drug; Drosophila; Electric Conductivity; Habituation, Psychophysiologic; Ion Channel Gating; Ion Channels; Monoterpenes; Nitriles; Odorants; Olfactory Receptor Neurons; Patch-Clamp Techniques; Rats; Rats, Wistar; Reaction Time; Signal Transduction; Terpenes

The ability of the turtle olfactory system to discriminate between various odorants that increase levels of adenosine 3',5'-cyclic monophosphate (cAMP) and inositol trisphosphate (IP3) in the olfactory bulb was examined by the cross-adaptation technique and analyzed by multidimensional scaling. The mean values of the degree of discrimination among the IP3-increasing odorants were higher than those among the cAMP-increasing odorants, and were similar to those between cAMP- and IP3-increasing odorants, suggesting that the features of the receptors of cAMP-increasing odorants are different from those which respond to IP3-increasing odorants. Analysis by multidimensional scaling suggested that differences in second messenger pathways are not related to detecting odor quality in the turtle olfactory system.

Topics: Acyclic Monoterpenes; Animals; Cyclic AMP; Discrimination, Psychological; Hemiterpenes; Inositol 1,4,5-Trisphosphate; Nitriles; Odorants; Olfactory Bulb; Pentanoic Acids; Pyrrolidines; Receptors, Odorant; Terpenes; Turtles

Odorant responses of isolated olfactory neurons from the toad Caudiverbera caudiverbera were monitored by using patch-clamp techniques. Depending on the stimulus, the same neuron responded with an increase or a decrease in action potential firing. Odorants that activate the cAMP cascade in olfactory cilia increased electrical activity, caused membrane depolarization, and triggered inward currents. In contrast, odorants that do not activate the cAMP cascade inhibited electrical activity, produced membrane hyperpolarization, and activated outward currents in a dose-dependent fashion. Such currents were carried by K+ and blocked by tetraethylammonium. Similar currents were recorded from Xenopus laevis. Our results suggest that this K+ current is responsible for odorant-induced inhibition of action potential firing in olfactory neurons.

Topics: Acyclic Monoterpenes; Animals; Anura; Dose-Response Relationship, Drug; Electric Stimulation; Ethylamines; Hemiterpenes; In Vitro Techniques; Membrane Potentials; Nitriles; Odorants; Olfactory Receptor Neurons; Pentanoic Acids; Potassium Channels; Pyrazines; Terpenes; Xenopus laevis