Purinergic (P2) receptors for extracellular adenosine triphosphate (ATP) are widely distributed throughout the body where they play diverse roles in cell signalling. P2Y receptors are metabotropic receptors that are also able to respond to ADP and uridine nucleotides, mobilising intracellular Ca2+ via the production of inositol 1,4,5-triphosphate. Ionotropic P2X receptors respond to physiological ATP and have varying degrees of Ca2+ permeability. P2Y1 receptors have previously been implicated in exocrine glands where they are thought to play a developmental role in salivary gland. The potential for purinergic signalling in the pancreas is great since ATP is a ubiquitous neuronal co-transmitter and millimolar concentrations of ATP are found in pancreatic zymogen granules. Purinergic signalling is implicated in exocrine pancreas pathophysiology since P2Y2, P2X7 and the ectonucleotidase CD39 are all upregulated in pancreatitis and pancreatic cancer and CD39 expression levels correlate with long term disease survival. The mouse is frequently used in models of pancreas pathophysiology, but the role of purinergic signalling in the mouse exocrine pancreas is unreported. Experiments were carried out on acutely isolated pancreatic acinar cells from C57BL6 mice, killed by cervical dislocation in accordance with UK Schedule 1 regulation of the Animal (Scientific Procedures) Act, 1986. Intracellular Ca2+-responses were measured by loading cells with Fura-2. We observed in adult animals only a minority (34 ± 4 %; N = 17) of pancreatic acinar cells responded to 100 µM ATP, whilst 19 % of cells responded to ADP and 8 % to UTP. In the absence of extracellular Ca2+, ATP responses were maintained. However no cells responded to ATP in the presence of extracellular Ca2+, but not in its absence; suggesting there were no functional P2X receptors at the plasma membrane. The proportion of cells responding to ATP increased to 90 ± 4 % (N = 7) when acinar cells were isolated from juvenile (6-18 days) mice, suggesting a developmental role for purinergic signalling in exocrine pancreas. In juvenile animals 87 % of cells responded to ADP, and 79 % responded to 100 nM MRS2365 a specific agonist of P2Y1 receptors. This response could be blocked by 100 nM MRS2500 a specific P2Y1 antagonist. Taken together these results suggest the developmental expression of P2Y1 receptors in pancreatic acinar cells. We also found in these cells that P2Y1 receptors were functionally coupled to enzyme secretion via the detection of extracellular amylase activity (with fluorescent BIODIPY-DQ starch dye) following P2Y1 receptor activation. These results show P2Y1 receptors are developmentally regulated in pancreatic acinar cells and suggests P2Y1 receptors play an important role in exocrine gland maturation.