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J Neurophysiol. 1997 Jun;77(6):3391-5.

Mg2+ inhibition of ATP-activated current in rat nodose ganglion neurons: evidence that Mg2+ decreases the agonist affinity of the receptor.

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Laboratory of Molecular and Cellular Neurobiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892-8205, USA.


The effect of Mg2+ on ATP-activated current in rat nodose ganglion neurons was investigated with the use of the whole cell patch-clamp technique. Mg2+ decreased the amplitude of ATP-activated current in a concentration-dependent manner over the concentration range of 0.25-8 mM, with a 50% inhibitory concentration value of 1.5 mM for current activated by 10 microM ATP. Mg2+ shifted the ATP concentration-response curve to the right in a parallel manner, increasing the 50% effective concentration value for ATP from 9.2 microM in the absence of added Mg2+ to 25 microM in the presence of 1 mM Mg2+. Mg2+ increased the deactivation rate of ATP-activated current without changing its activation rate. The observations are consistent with an action of Mg2+ to inhibit ATP-gated ion channel function by decreasing the affinity of the agonist binding site on these receptors.

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