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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Cyclic AMP, GTP-Binding Proteins, Ganglia, Spinal, Patch-Clamp Techniques, Rats, Rats, Wistar, Receptors, Purinergic P2, Receptors, Purinergic P2X3, Second Messenger Systems, Sensory Receptor Cells.
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Does extracellular cAMP inhibit P2X receptors in rat sensory neurones through G protein-mediated mechanism? Context: To identify the mechanisms of P2X(3) receptor inhibition by extracellular cyclic adenosine monophosphate (cAMP) in rat dorsal root ganglion (DRG) neurones. Whole-cell currents were measured in cultured DRG neurones using the combination of voltage and concentration clamp. We have found that extracellular cAMP inhibits P2X(3)-mediated currents in a concentration- and use-dependent manner. The P2X(3) currents, activated by ATP applied every 4 min, were inhibited by 55% in the presence of 10 microm cAMP and by 81% in the presence of 30 microm cAMP. At 8 min interval between ATP applications the same concentration of cAMP did not alter the currents. Addition of 0.5 mm of guanosine 5'-O-(2-thiodiphosphate) to intracellular solution blocked the inhibitory action of cAMP. The inhibitory effects of cAMP were not mimicked by extracellular application of 30 mum adenosine.
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In this paper, we demonstrate, for the first time, that extracellular application of cAMP to rat sensory neurones inhibits P2X(3) receptors via a G protein-coupled mechanism in a use-dependent manner, thus indicating the neuronal expression of specific plasmalemmal cAMP receptor. Final Decision: yes