High-gain, low-noise amplification in olfactory transduction.
It is desirable that sensory systems use high-gain, low-noise amplification to convert weak stimuli into detectable signals. Here it is shown that a pair of receptor currents underlying vertebrate olfactory transduction constitutes such a scheme. The primary receptor current is an influx of Na+ and Ca2+ through cAMP-gated channels in the olfactory cilia. External divalent cations improve the signal-to-noise properties of this current, reducing the mean current and the current variance. As Ca2+ enters the cilium, it gates Cl- channels, activating a secondary depolarizing receptor current. This current amplifies the primary current, but introduces little additional noise. The system of two currents plus divalent cations in the mucus produces a large receptor current with very low noise.
Kleene
S J
SJ
Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati, Ohio 45267-0521, USA. steve@syrano.acb.uc.edu
D000818:Animals; D002118:Calcium / Q000502:physiology; D018118:Chloride Channels / Q000502:physiology; D002923:Cilia / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D008564:Membrane Potentials; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D011894:Rana pipiens; D015398:Signal Transduction; D012903:Smell / Q000502:physiology*
D018118:Chloride Channels; D000242:Cyclic AMP; D002118:Calcium