Complex sentence: Menthol can activate the TRPM8 channel in this way and since this channel is epressed in neurones whose physiologically role it is to signal cooling, menthol applied to various bodily surface evokes a sensations of cooling.
Split into simpler sentences: Menthol can activate the TRPM8 channel in this way. Since the TRPM8 is expressed in neurones whose physiological role is to signal cooling, menthol applied to various bodily surface evokes a sensation of cooling.