Dynamics and adaptation in the olfactory and phototransduction pathways

Due to their function of “probes” of external stimuli, sensory systems have to be able to respond appropriately to a wide range of amplitudes of the input signal. The process by means of which they adjust their sensitivity to a stimulus is called adaptation. In the first part of the thesis we focus on the study of the olfactory transduction pathway, explaining the adaptation exhibited by this system, and introducing a model able to reproduce the features of the biological response. We then consider data obtained from phototransduction experiments and compare their properties with those of the olfactory system, unveiling a possible general mechanism used by these two pathways to achieve adaptation. Finally a detailed study of one of the ion channels involved in the olfactory transduction pathway, the calcium-activated chloride channel, is presented. We suggest a Markov scheme explaining the modulation of the activity of the channel by the transmembrane voltage and the calcium concentration.