In order to understand how olfactory stimuli are encoded and processed in the brain, it is important to build a computational model for olfactory receptor neurons (ORNs). Here, we present a simple and reliable mathematical model of a moth ORN generating spikes. The model incorporates a simplified description of the chemical kinetics leading to olfactory receptor activation and action potential generation. We show that an adaptive spike threshold regulated by prior spike history is an effective mechanism for reproducing the typical phasic-tonic time course of ORN responses. Our model reproduces the response dynamics of individual neurons to a fluctuating stimulus that approximates odorant fluctuations in nature. The parameters of the spike threshold are essential for reproducing the response heterogeneity in ORNs. The model provides a valuable tool for efficient simulations of olfactory circuits.

• Klíčová slova
• adaptive threshold, integrate-and-fire model, olfactory receptor neuron,
• MeSH
• akční potenciály fyziologie   MeSH
• biologické modely MeSH
• čichové buňky účinky léků   fyziologie   MeSH
• elektrofyziologické jevy MeSH
• fyziologická adaptace * MeSH
• můry fyziologie   MeSH
• sexuální lákadla farmakologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• sexuální lákadla MeSH

The concept of coding efficiency holds that sensory neurons are adapted, through both evolutionary and developmental processes, to the statistical characteristics of their natural stimulus. Encouraged by the successful invocation of this principle to predict how neurons encode natural auditory and visual stimuli, we attempted its application to olfactory neurons. The pheromone receptor neuron of the male moth Antheraea polyphemus, for which quantitative properties of both the natural stimulus and the reception processes are available, was selected. We predicted several characteristics that the pheromone plume should possess under the hypothesis that the receptors perform optimally, i.e., transfer as much information on the stimulus per unit time as possible. Our results demonstrate that the statistical characteristics of the predicted stimulus, e.g., the probability distribution function of the stimulus concentration, the spectral density function of the stimulation course, and the intermittency, are in good agreement with those measured experimentally in the field. These results should stimulate further quantitative studies on the evolutionary adaptation of olfactory nervous systems to odorant plumes and on the plume characteristics that are most informative for the 'sniffer'. Both aspects are relevant to the design of olfactory sensors for odour-tracking robots.

• MeSH
• akční potenciály fyziologie   MeSH
• čich fyziologie   MeSH
• čichové buňky fyziologie   MeSH
• čichové dráhy fyziologie   MeSH
• modely neurologické * MeSH
• můry fyziologie   MeSH
• počítačová simulace MeSH
• sexuální lákadla fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• sexuální lákadla MeSH

The first step of olfactory transduction consists of the interaction of odorant molecules with receptor proteins. This interaction can be described either as a single-step reaction (binding only) or as a double-step one (binding and activation). The number of bound or activated receptors is analyzed as a function of the external concentration of odorant molecules in two models of the neuron environment. In one model the odorant molecules can freely access and leave the vicinity of receptors, whereas in the other a real perireceptor space, partly isolated from the external environment is considered. The steady state and time variable responses to the stimulus are investigated.

• MeSH
• čichové buňky fyziologie   MeSH
• modely neurologické MeSH
• odoranty * MeSH
• receptory pachové fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• receptory pachové MeSH

Monoaminergic neurotransmitter 5-hydroxytryptamine (5-HT), also known as serotonin, plays important roles in modulating the function of the olfactory system. However, thus far, the knowledge about 5-HT and its receptors in olfactory receptor neurons (ORNs) and their physiological role have not been fully characterized. In the present study, reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed the presence of 5-HT(1A) and 5-HT(1B) receptor subtypes in mouse olfactory epithelium at the mRNA level. With subtype selective antibodies and standard immunohistochemical techniques, both receptor subtypes were found to be positively labeled. To further elucidate the molecular mechanisms of 5-HT act on the peripheral olfactory transduction, the whole-cell patch clamp techniques were used on freshly isolated ORNs. We found that 5-HT decreased the magnitude of outward K(+) current in a dose-dependent manner and these inhibitory effects were markedly attenuated by the 5-HT(1A) receptor blocker WAY-100635 and the 5-HT(1B) receptor antagonist GR55562. These data suggested that 5-HT may play a role in the modulation of peripheral olfactory signals by regulating outward potassium currents, both 5-HT(1A) and 5-HT(1B) receptors were involved in this regulation.

• MeSH
• antagonisté serotoninových receptorů 5-HT1 farmakologie   MeSH
• čichové buňky účinky léků   metabolismus   MeSH
• draslíkové kanály účinky léků   metabolismus   MeSH
• membránové potenciály MeSH
• messenger RNA metabolismus   MeSH
• myši MeSH
• receptor serotoninový 5-HT1A účinky léků   genetika   metabolismus   MeSH
• receptor serotoninový 5-HT1B účinky léků   genetika   metabolismus   MeSH
• serotonin metabolismus   MeSH
• signální transdukce MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antagonisté serotoninových receptorů 5-HT1 MeSH
• draslíkové kanály MeSH
• messenger RNA MeSH
• receptor serotoninový 5-HT1A MeSH
• receptor serotoninový 5-HT1B MeSH
• serotonin MeSH

Signal processing in the olfactory system is initiated by binding of odorant molecules to receptor molecules embedded in the membranes of sensory neurons. Most analyses of odorant-receptor interaction focus on one or more types of odorants binding with one type of receptors. Here, two basic models of this first step are investigated under the assumption that the population of receptors is not homogenous and is characterized by different activation/deactivation rates. Both, discrete and continuous variation of the rates are considered. The steady-state characteristics of the models are derived. In addition, time to crossing a threshold, defined as a response time, is also investigated. The achieved results are compared with those valid for models with the homogenous population of receptors and interpreted in terms of information coding. The obvious implications of the modeling study--that the heterogeneity of receptors enlarges the coding range and increases the sensitivity of the system--are quantified.

• MeSH
• biologické modely * MeSH
• čichové buňky metabolismus   fyziologie   MeSH
• hmyz fyziologie   MeSH
• kinetika MeSH
• receptory pachové metabolismus   fyziologie   MeSH
• systémy druhého messengeru fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• receptory pachové MeSH

The efficient coding hypothesis predicts that sensory neurons adjust their coding resources to optimally represent the stimulus statistics of their environment. To test this prediction in the moth olfactory system, we have developed a stimulation protocol that mimics the natural temporal structure within a turbulent pheromone plume. We report that responses of antennal olfactory receptor neurons to pheromone encounters follow the temporal fluctuations in such a way that the most frequent stimulus timescales are encoded with maximum accuracy. We also observe that the average coding precision of the neurons adjusted to the stimulus-timescale statistics at a given distance from the pheromone source is higher than if the same encoding model is applied at a shorter, non-matching, distance. Finally, the coding accuracy profile and the stimulus-timescale distribution are related in the manner predicted by the information theory for the many-to-one convergence scenario of the moth peripheral sensory system.

• MeSH
• čichové buňky fyziologie   MeSH
• čichové dráhy fyziologie   MeSH
• elektrofyziologické jevy MeSH
• feromony fyziologie   MeSH
• můry fyziologie   MeSH
• neurony aferentní fyziologie   MeSH
• pravděpodobnost MeSH
• reprodukovatelnost výsledků MeSH
• statistické modely MeSH
• tykadla členovců fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• feromony MeSH

The olfactory system in insects has evolved to process the dynamic changes in the concentration of food odors or sex pheromones to localize the nutrients or conspecific mating partners. Experimental studies have suggested that projection neurons (PNs) in insects encode not only the stimulus intensity but also its rate-of-change (input gradient). In this study, we aim to develop a simple computational model for a PN to understand the mechanism underlying the coding of the rate-of-change information. We show that the spike frequency adaptation is a potential key mechanism for reproducing the phasic response pattern of the PN in Drosophila. We also demonstrate that this adaptation mechanism enables the PN to encode the rate-of-change of the input firing rate. Finally, our model predicts that the PN exhibits the intensity-invariant response for the pulse and ramp odor stimulus. These results suggest that the developed model is useful for investigating the coding principle underlying olfactory information processing in insects.

• Klíčová slova
• Input rate-of-change, Insect olfactory system, Sensory coding, Spike frequency adaptation,
• MeSH
• čich fyziologie   MeSH
• čichové buňky * fyziologie   MeSH
• čichové dráhy * fyziologie   MeSH
• Drosophila MeSH
• hmyz MeSH
• interneurony MeSH
• odoranty MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Eurasian spruce bark beetle Ips typographus, a natural part of forest ecosystems, is a major threat to Norway spruce forests during outbreaks. Olfaction plays a crucial role in the survival and range expansion of these beetles, amid forest disturbances and climate change. As the current management strategies are suboptimal for controlling outbreaks, the reverse chemical ecology approaches based on pheromone receptors offer promising alternatives. While the search for pheromone receptors is in progress, recently found chromosomal inversions indicates signs of adaptation in this species. Our attempts to characterise one of the highly expressed odorant receptors, ItypOR33, located in an inversion, led to the discovery of polymorphic variants distributed with similar frequency across 18 European populations. Deorphanizing ItypOR33 and its variant ItypOR33a using the Drosophila empty-neuron system (DeNS) revealed ItypOR33 tuned to amitinol, a heterospecific pheromone component in Ips spp., whereas its variant tuned to (S)-(-)-ipsenol, a conspecific pheromone component of I. typographus. The in silico approaches revealed the structural basis of variations by predicting putative ligand-binding sites, tunnels and ligand-receptor interactions. However, no sex-specific differences were found in the ItypOR33 expression, and its ligand amitinol elicited behavioural and electrophysiological responses. Reporting population-level functional olfactory polymorphisms for the first time in a non-model organism-bark beetles, provides key evidence for further exploring their survival and adaptation in forests. Additionally, these findings indicate potential long-term complexities of managing bark beetles in forests.

• Klíčová slova
• Drosophila empty‐neuron system, bark beetles, deorphanization, functional polymorphism, olfactory adaptation, pheromone receptor, population genomics,
• MeSH
• brouci * genetika   MeSH
• čich genetika   MeSH
• feromony genetika   MeSH
• polymorfismus genetický MeSH
• receptory pachové genetika   MeSH
• receptory pro feromony genetika   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Evropa MeSH
• Názvy látek
• feromony MeSH
• receptory pachové MeSH
• receptory pro feromony MeSH

Several models (concentration detectors and a flux detector) for coding of odor intensity in olfactory sensory neurons are investigated. Behavior of the system is described by different stochastic processes of binding the odorant molecules to the receptors and their activation. Characteristics how well the odorant concentration can be estimated from the knowledge of response, the number of activated neurons, are studied. The approach is based on the Fisher information and analogous measures. These measures of optimality are computed and applied to locate the odorant concentration which is most suitable for coding. The results are compared with the classical deterministic approach which judges the optimal odorant concentration via steepness of the input-output function.

• MeSH
• algoritmy MeSH
• čichové buňky fyziologie   MeSH
• kinetika MeSH
• lidé MeSH
• modely neurologické * MeSH
• odoranty MeSH
• receptory pachové fyziologie   MeSH
• signální transdukce * MeSH
• statistické modely MeSH
• stochastické procesy MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• receptory pachové MeSH

Olfactory sensitivity to odorant molecules is a complex biological function influenced by both endogenous factors, such as genetic background and physiological state, and exogenous factors, such as environmental conditions. In animals, this vital ability is mediated by olfactory sensory neurons (OSNs), which are distributed across several specialized olfactory subsystems depending on the species. Using the phosphorylation of the ribosomal protein S6 (rpS6) in OSNs following sensory stimulation, we developed an ex vivo assay allowing the simultaneous conditioning and odorant stimulation of different mouse olfactory subsystems, including the main olfactory epithelium, the vomeronasal organ, and the Grueneberg ganglion. This approach enabled us to observe odorant-induced neuronal activity within the different olfactory subsystems and to demonstrate the impact of environmental conditioning, such as temperature variations, on olfactory sensitivity, specifically in the Grueneberg ganglion. We further applied our rpS6-based assay to the human olfactory system and demonstrated its feasibility. Our findings show that analyzing rpS6 signal intensity is a robust and highly reproducible indicator of neuronal activity across various olfactory systems, while avoiding stress and some experimental limitations associated with in vivo exposure. The potential extension of this assay to other conditioning paradigms and olfactory systems, as well as its application to other animal species, including human olfactory diagnostics, is also discussed.

• Klíčová slova
• 3Rs, Grueneberg ganglion, environmental factors, human, mouse, neuronal activity, olfaction, olfactory subsystems, rpS6,
• MeSH
• čich fyziologie   MeSH
• čichová sliznice metabolismus   MeSH
• čichové buňky * metabolismus   fyziologie   MeSH
• fosforylace MeSH
• lidé MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• odoranty analýza   MeSH
• ribozomální protein S6 * metabolismus   MeSH
• vomeronazální orgán metabolismus   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ribozomální protein S6 * MeSH