Details

Autor(en) / Beteiligte

• Guarracino, Juan F.
• Cinalli, Alejandro R.
• Veggetti, Mariela I.
• Losavio, Adriana S.

Titel

Endogenous purines modulate K+‐evoked ACh secretion at the mouse neuromuscular junction

Ist Teil von

• Journal of neuroscience research, 2018-06, Vol.96 (6), p.1066-1079

Ort / Verlag

United States: Wiley Subscription Services, Inc

Erscheinungsjahr

2018

Quelle

Access via Wiley Online Library

Beschreibungen/Notizen

• 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 P2Y13 and A1, A2A, and A3 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 P2Y13 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 A1, A3, and A2A 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 P2Y13 and A1 and A3 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 A2A 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. At the mammalian neuromuscular junction, ATP is co‐released with the neurotransmitter ACh, and once in the synaptic cleft, it is hydrolyzed to adenosine. We report that, when motor nerve terminals are depolarized by increasing [K+]o, there is a sequence of activation of presynaptic purinergic receptors that are able to modulate neurosecretion.