Nitric oxide is an intercellular signalling molecule which has the potential to amplify intracellular Ca²⁺ signalling in salivary gland cells by increasing cADPr levels and thus the contribution of ryanodine receptors to Ca²⁺-induced Ca²⁺ release (CICR). Sjögren’s syndrome is an autoimmune disease in which there is a failure of Ca²⁺ dependent fluid secretion. Paradoxically, NO levels are known to be elevated in the salivary glands of Sjögren’s syndrome patients. (Kontinnen et al 1997) We have investigated the effects of acute and chronic exposure to elevated levels of NO using the NO donor S-nitroso-N-acetyl penicillamine (SNAP). CD-1 mice were humanely killed by stunning and cervical dislocation. Submandibular glands were excised, acinar cells were isolated by collagenase digestion (200units/ml, Worthington) and cultured for 24 hours at 37^o on matrigel (Becton Dickinson, UK) coated glass coverslips in serum free 50:50 Dulbecco’s MEM:F12 medium containing antibiotics and antimycotics (Life Technologies UK). Agonist evoked changes in [Ca²⁺]_i were imaged (Cairn Research, UK) in acinar cells loaded with fura-2 AM. We found that acute application of SNAP at 100 μM caused significant amplification of threshold ACh responses, consistent with a cADPr mediated amplification of the Ca²⁺ signal (Harmer et al 2001). Sustained application of SNAP lead to a slow ramp in ‘resting’ [Ca²⁺]_i and ultimately to insensitivity to ACh stimulation. These data suggest that prolonged exposure to elevated levels of NO render acinar cells less sensitive to ACh stimulation. These data are consistent with our previous observation that human labial gland acinar cells taken from Sjögren’s syndrome patients show reduced sensitivity to stimulation by muscarinic agonists (Dawson et al 2001). The most straightforward explanation of this phenomenon is that NO leads to depletion of the intracellular Ca²⁺ stores.