The focus of the work proposed in this application is to gain a comprehensive understanding of the involvement of extracellular ATP and related compounds (e.g. ADP, AMP and adenosine) in urinary bladder neuroeffector processes. In the mammalian urinary bladder ATP is believed to act in conjunction with other substances as an excitatory neurotransmitter. The neuronal source of ATP (i.e., adrenergic, cholinergic or non-adrenergic, non-cholinergic nerves), however, has not been established nor has the possibility that ATP can be released from extraneuronal sites, as for example, from the smooth muscle or urothelium. Studies will be conducted to establish the site(s) of origin of ATP and other adenine nucleosides and nucleotides. A poorly understood feature of the extracellular actions of ATP is its ability to potentiate the actions of other smooth muscle agonists such as other neurotransmitters or mast cell products. The mechanism of this potentiation will be probed by studying the effects of ATP alone and in combination with histamine, leukotriene and acetylcholine on intracellular calcium, phosphatydlinositol turnover and myosin phosphorylation. In addition to postjunctional actions, ATP exerts prejunctional actions. The nucleotide can modify the release of neurotransmitters although whether this occurs with the autonomic nerves of the urinary bladder is not well known nor is there any definitive information about the type of receptor with which ATP acts to reduce transmitter release. The hypothesis will be tested that ATP acts per se, without conversion to adenosine, on a novel P3 receptor. Once the involvement of adenine nucleotides and nucleosides in normal bladder has been more clearly defined, the actions of these purines in bladders taken from ovalbumin sensitized guinea-pigs will be examined. These bladders exhibit an increased number of mast cells, a situation frequently reported to occur in patients suffering from interstitial cystitis.