The concept of purinergic signalling arose from experiments designed to find the identity of the non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmitter in the gut.1 However, it has taken many years for the more general importance of the various roles of ATP as a physiological messenger in the gut to be recognised. Later, after the concept of co-transmission was established, ATP, nitric oxide and vasoactive intestinal polypeptide were recognised as co-transmitters in NANC nerves, although the proportions vary in different gut regions. Following cloning experiments in the early 1990s, four subtypes of P1 (adenosine) receptors, seven subtypes of P2X ion channel receptors and eight subtypes of P2Y G-protein-coupled receptors have been recognised.2 Many of these purinoceptor subtypes have been identified on the myenteric, submucosal motor, sensory and interneurons involved in synaptic …