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Endogenous purines modulate K + ‐evoked ACh secretion at the mouse neuromuscular junction
Author(s) -
Guarracino Juan F.,
Cinalli Alejandro R.,
Veggetti Mariela I.,
Losavio Adriana S.
Publication year - 2018
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.24223
Subject(s) - adenosine , acetylcholine , neuromuscular junction , chemistry , purinergic receptor , inhibitory postsynaptic potential , adenosine a1 receptor , synaptic cleft , neuromuscular transmission , neurotransmitter , biochemistry , adenosine receptor , endocrinology , biology , receptor , agonist , neuroscience
At the mouse neuromuscular junction, adenosine triphosphate (ATP) is co‐released with the neurotransmitter acetylcholine (ACh), and once in the synaptic cleft, it is hydrolyzed to adenosine. Both ATP/adenosine diphosphate (ADP) and adenosine modulate ACh secretion by activating presynaptic P2Y 13 and A 1 , A 2A , and A 3 receptors, respectively. To elucidate the action of endogenous purines on K + ‐dependent ACh release, we studied the effect of purinergic receptor antagonists on miniature end‐plate potential (MEPP) frequency in phrenic diaphragm preparations. At 10 mM K + , the P2Y 13 antagonist N‐[2‐(methylthio)ethyl]‐2‐[3,3,3‐trifluoropropyl]thio‐5′‐adenylic acid, monoanhydride with (dichloromethylene)bis[phosphonic acid], tetrasodium salt (AR‐C69931MX) increased asynchronous ACh secretion while the A 1 , A 3 , and A 2A antagonists 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX), (3‐Ethyl‐5‐benzyl‐2‐methyl‐4‐phenylethynyl‐6‐phenyl‐1, 4‐(±)‐dihydropyridine‐3,5‐, dicarboxylate (MRS‐1191), and 2‐(2‐Furanyl)‐7‐(2‐phenylethyl)‐7H‐pyrazolo[4,3‐e][1,2,4]triazolo[1,5‐c]pyrimidin‐5‐amine (SCH‐58261) did not modify neurosecretion. The inhibition of equilibrative adenosine transporters by S‐(p‐nitrobenzyl)‐6‐thioinosine provoked a reduction of 10 mM K + ‐evoked ACh release, suggesting that the adenosine generated from ATP is being removed from the synaptic space by the transporters. At 15 and 20 mM K + , endogenous ATP/ADP and adenosine bind to inhibitory P2Y 13 and A 1 and A 3 receptors since AR‐C69931MX, DPCPX, and MRS‐1191 increased MEPP frequency. Similar results were obtained when the generation of adenosine was prevented by using the ecto‐5′‐nucleotidase inhibitor α,β‐methyleneadenosine 5′‐diphosphate sodium salt. SCH‐58261 only reduced neurosecretion at 20 mM K + , suggesting that more adenosine is needed to activate excitatory A 2A receptors. At high K + concentration, the equilibrative transporters appear to be saturated allowing the accumulation of adenosine in the synaptic cleft. In conclusion, when motor nerve terminals are depolarized by increasing K + concentrations, the ATP/ADP and adenosine endogenously generated are able to modulate ACh secretion by sequential activation of different purinergic receptors.