Transduction and adaptation in sensory receptor cells

Abstract

Sensory transduction shares common features in widely different sensory modalities. The purpose of this article is to examine the similarities and differences in the underlying mechanisms of transduction in the sensory receptor cells for vision, olfaction, and hearing. One of the major differences between the systems relates to the nature of the stimulus. In both the visual and olfactory systems a quantal mechanism of detection is possible, because the absorption of a photon or the binding of an odorant molecule provides an energy change significantly greater than the thermal noise in the receptor molecule. In hearing, on the other hand, the energy of a phonon is far lower, and detection occurs by a "classical" mechanism. For vertebrate photoreceptors and olfactory receptor cells, sensory transduction employs a G protein cascade that is remarkably similar in the two cases, and that is closely homologous to other G protein signaling cascades. For auditory and vestibular hair cells, transduction operates via a mechanism of direct coupling of the stimulus to ion channels, in a manner reminiscent of the direct gating of post-synaptic ion channels in various synaptic mechanisms. The three classes of sensory receptor cell share similarities in their mechanisms of adaptation, and it appears in each case that cytoplasmic calcium concentration plays a major role in adaptation.

Fold-change detection and scalar symmetry of sensory input fields

“…Examples include sensory modalities such as auditory searches for sound sources and olfactory searches for odorant sources (47)(48)(49)(50). Experiments can investigate this on several levels: whether search movement is independent of signal source strength, whether the input-output relationship shows FCD, and whether the molecular mechanism follows the present conditions for FCD.…”

Ca2+–Calmodulin Feedback Mediates Sensory Adaptation and Inhibits Pheromone-Sensitive Ion Channels in the Vomeronasal Organ

“…A fit of the data points using the Hill equation revealed a K 1/2 value of 540 nM and a Hill coefficient of 2. If this inhibitory effect of CaM is involved in sensory adaptation of VSNs, the reduction in current amplitude should reflect a shift of the dynamic range of the SAG conductance toward higher SAG concentrations (Torre et al, 1995;Menini, 1999;. If so, Ca 2ϩ -CaM-induced channel inhibition would be most effective with SAG concentrations near half-maximal channel activation (EC 50 ), whereas the effect should be reduced or absent when saturating SAG concentrations are used.…”

“…To examine this question, we first used local field potential recordings [the electro-vomeronasogram (EVG)] and measured electrophysiological responses to natural urine stimuli or single pheromone ligands from the microvillous layer of an intact VNO preparation , 2004Del Punta et al, 2002;Leypold et al, 2002). In OSNs, odor adaptation is evident as a decrease in sensitivity arising from prolonged or previous odor exposure (Torre et al, 1995;Munger et al, 2001;Song et al, 2008). We therefore applied single or paired pulses of chemostimuli.…”

Loss of gustatory responses to pyrrolizidine alkaloids after their extensive ingestion in the polyphagous caterpillar Estigmene acrea

“…Tests of insects with seneciphylline N-oxide immediately after such a 10-min exposure was terminated indicated that sensory recovery, or disadaptation, was quite rapid and was complete after just 20·min (Fig.·7). Such a time frame is not unusual in studies of adaptation (Torre et al, 1995).…”