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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Semin Cell Dev Biol. 2012 Dec 20;24(1):71–79. doi: 10.1016/j.semcdb.2012.12.002

Fig. 4.

Fig. 4

ATP exerts positive feedback via presynaptic autocrine receptors to boost its secretion during taste stimulation. This diagram shows a Receptor (Type II) cell releasing ATP next to a sensory afferent fiber. Receptor (Type II) taste cells secrete ATP likely via pannexin 1 gap junction hemichannels in the plasma membrane (Panx1). ATP excites postsynaptic targets as well as autocrine P2X2 and P2Y1 receptors on the Type II cell itself. Stimulation of P2X2 and P2Y1 receptors initiates Ca2+ influx and Ca2+ release from intracellular stores, respectively. Both these actions increase intracellular [Ca2+] which further enhances Panx1 activity and boosts ATP release. Genetic elimination of P2X2 (P2X2 knockout) greatly reduces taste-evoked ATP secretion from Receptor and taste reception [50,66].