All taste fibers
express ionotropic purinergic (P2X) receptors (Bo et al., 1999; Ishida et al., 2009) that are required for transmission from taste receptor cells to the afferent nerves; genetic deletion or pharmacological blockade of the P2X2 and P2X3 receptors expressed by the gustatory nerve fibers eliminates chorda tympani nerve responses to all taste stimuli (Finger et al., 2005; Ohkuri et al., 2012; Jaber et al., 2014; Vandenbeuch et al., 2015).