Receptor heterogeneity and its effect on sensitivity and coding range in olfactory sensory neurons

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.