A Mathematical Model of ATP Secretion by Type II Taste Cells

The functional unit of the taste system in mammals is the taste bud, which is a heterogeneous population of 50–80 different cells, including types I, II, and III taste cells. Apart from recognizing taste molecules, taste cells encode sensory information in the form of stimulus-dependent secretion of the afferent neurotransmitter stimulating the taste nerves. Afferent neurotransmission in type II taste cells has many characteristics setting them apart from other exteroreceptor cells operating in vertebrate sensory organs. Thus, type II cells use ATP as neurotransmitter, released via ATP-permeable ion channels. Although taste cells lack axons, type II cells are electrically excitable and the neurotransmitter secretion process is controlled by an action potential. We developed a mathematical model of ATP secretion through a potential-dependent ATP-permeable ion channel and analyzed the potential dependence of secretion in the steady-state case and on stimulation of the cell with pulses. The patterns of ATP secretion found here led to the conclusion that as compared with control of ATP release by a graduated receptor potential, the electrical excitability of taste cells widens the dynamic range of perceived taste stimuli and provides greater reliability of synaptic transmission and confers quantum properties upon it.