Projects / Programmes
Filiform sensilla in the bug Pyrrhocoris apterus: a model system for biophysical and physiological studies of mechanoreception
| Code |
Science |
Field |
Subfield |
| 1.03.01 |
Natural sciences and mathematics |
Biology |
Zoology and zoophysiology |
| Code |
Science |
Field |
| B360 |
Biomedical sciences |
Animal physiology |
| Code |
Science |
Field |
| 1.06 |
Natural Sciences |
Biological sciences |
filiform sensilla, Pyrrhocoris apterus, extracellular registration, nerve impulses, spikes, mechanoreception, mechanosensitive ion channels, mechanotransduction, sensory adaptation, spike generator, mathematical model, membrane potential time course, spontaneous activity, active mechanical signal amplification, noninvasive methods
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
24293 |
PhD Aleš Škorjanc |
Biology |
Head |
2011 - 2013 |
42 |
Organisations (1)
Abstract
Development of genetic tools has tremendously accelerated the research of mechanoreception in recent years. Insect sensilla have taken one of the central roles in this development. Due to the inaccessibility of most mechanosensitive cells to direct measurements a synthesis of mathematical modelling and physiological experiments proved to be essential. We present filiform sensilla of the bug Pyrrhocoris apterus as a model system especially suitable for such approach due to the low number of sensory units, which enables a controlled stimulation and a straightforward registration of a single unit activity. In this project we will combine precisely defined stimulation, extracellular registration of spikes, mathematical modelling and theoretical analysis to create (1) a mathematical MODEL OF THE SENSORY PROCESS IN FILIFORM SENSILLA. The model will give us an insight into the quantitative relations between individual elements and phases of the process, which is otherwise not possible without direct measurements. It will have 3 parts: transformation of the sensory hair deflection into sensory dendrite deformation (modelled by a harmonic oscillator coupled with a nonlinear spring), transduction of the mechanical stimulus into receptor current (modelled by the basic two-stage model of mechanosensitive channels), and transformation of the receptor current into spike train (modelled by a phenomenological model of spike generator adaptation that is defined by a spike frequency response to standard stimuli). We will optimize parameters of the model and infer about the sensory process from their values. We will also measure mechanical properties of sensilla with laser vibrometer to test for ACTIVE MECHANICAL AMPLIFICATION OF THE SIGNAL, seen in fruit fly hearing. We will modify the model accordingly, if present. (2) We will DEVELOP A SIMPLE UNIVERSAL METHOD FOR RECONSTRUCTING MEMBRANE POTENTIAL TIME COURSE from extracellularly recorded spikes using a simple test stimulus. With the stimulus repeatedly applied to a spontaneously active cell we will determine the response latency in different phases of interspike time interval. Our preliminary simulations of the method on standard model neurons have shown that the latency depends linearly on the relative distance of the potential from the spike initiation threshold therefore allowing for an estimation of the relative value of the potential. The method will be tested with intracellular recordings on layer-5 pyramidal cells of young rats in vitro. With this method it will be possible to infer about the integration regime of the membrane potential and possibly adaptation processes and receptor current noise level in different types of sensilla. It will also allow for distinguishing sub- and superthreshold regime of spike discharge, which is important for understanding information encoding in the presence of noise. Development of such method would have more general implications since it could be used for studying a wide variety of cells. (3) We will CHARACTERIZE THE SPONTANEOUS ACTIVITY OF FILIFORM SENSILLA in different species of bugs (Heteroptera). Although spontaneous activity is present in many cells, it has not received much attention in the scientific community. One of the surprising discoveries in filiform sensilla of P. apterus is regulation of the activity on a very precise specific absolute level in different sensilla types. By comparing the activity in different morphs of P. apterus and in animals from a wider European region and between different species of bugs we will find out whether maintaining the activity on a specific absolute level is a more general principle. This would shed a new light on the function of spontaneous activity and motivate further research of its mechanisms.
Significance for science
The study of mechanoreception gained a new momentum with the development of molecular biology. Insect sensilla played a crucial role in this development. However, despite new insights the overall understanding of the sensory process of sensilla remains incomplete. In this project we therefore made an integral study of filiform sensilla in the bug Pyrrhocoris apterus. We developed a mathematical model of the sensillum, which explains the non-linearity of its response and the origin of fast and slow sensory adaptation. We experimentally showed that the location of sensilla on the abdomen of the bug allows for optimal detection of air-flow, and that the physiological response of the sensillum is adapted to the high-pass filter properties of the air-flow to hair-motion coupling. We also showed that the spontaneous activity of filiform sensilla is a precisely regulated process. The defined level of the activity plays an important role in the function of sensilla, which has not been known so far. We also developed a novel electrophysiological method for a reconstruction of the membrane potential time-course in sensory and neural cells, based on extracellular registration of nerve impulses. With this project ,we have therefore contributed to a better understanding of some basic problems of mechanoreception, and we have introduced the bug P. apterus as a potential model organism for the research of mechanosensitive sensilla.
Significance for the country
Bugs are a large group of insects, which includes some species that are becoming significant pests of crops in Slovenia. With increasing awareness of the danger of insecticides there is a need for a development of other means of pest control. One possible strategy is a development of repellents based on imitation of signals, created by the natural enemies of bugs. In this project, we measured the mechanical properties of filiformnih sensilla and the frequency properties of the air-flow to sensory hair-motion coupling. We have found that the latter correspond to the frequency characteristics of the air-flow oscillation generated by some of the natural enemies of bugs. We believe that these findings can contribute to the development of new repellents based on mechanical stimuli. Another accomplishment of this project with important implications for the development of Slovenia is a foundation of an international summer school for students "Sensory systems in natural environments". I founded the school with Prof. Jan Benda from the University of Tübingen in 2012. In 2013 the school was joined also by Prof. Michael Gebhardt from the Technical University of Munich. The goal of the school is to introduce students into the neurobiology research. In the school we focus on sensory systems of insects and their interaction with natural stimuli, to which the sensory systems have adapted. The first two weeks of the school take place in Slovenia and the last week in Germany. By joining the school the students gain knowledge in biophysics and physiology of sensory systems, electrophysiological methods and signal analysis and in mathematical modelling of sensory processes. They also gain some study abroad experience and make connections with other students and professors which is crucial for making a career in science. In 2013 the school became a part of the program in biology at the University of Ljubljana. This ensures not only an education of young scientists but also a close collaboration between the University of Tübingen, the Technical University of Munich and the University of Ljubljana.
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