Effect of adenosine triphosphate on the sensitivity of the nicotinic acetylcholine‐receptor in the bullfrog sympathetic ganglion cell

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Abstract
1 The effects of adenosine triphosphate (ATP) and related compounds on the sensitivity of the nicotinic acetylcholine (ACh)-receptor of bullfrog sympathetic ganglion cells were analysed electro physiologically. 2 ATP in concentrations between 0.05 and 2 mm increased the amplitudes of the potentials and currents induced by ACh, and carbachol-induced currents. 3 Compared with ATP, ADP was less potent in producing augmentation of the carbachol-induced current by one order of magnitude. AMP, cyclic AMP and adenosine had no appreciable effect. 4 Analysis of this ATP effect, based on Michaelis-Menten type kinetics, revealed that ATP increased the maximum response (Vmax) of the dose-response curve of ACh currents without an appreciable effect on the affinity (Km) of ACh for its receptor. 5 It is suggested that ATP increased the receptor sensitivity by acting on an allosteric site of the nicotinic ACh receptor-ionic channel complex which, thus, may be linked to an ATP receptor, probably of the P2-receptor type (Burnstock, 1981).