P2Y12 or 13 receptors are involved in the presynaptic inhibition induced by adenine nucleotides at the mouse neuromuscular junction

SILVANA DE LORENZO,; MARIELA VEGGETTI; MARÍA PAULA MAGARIÑOS; SALOMÓN MUCHNIK; ADRIANA LOSAVIO

Buenos Aires

Congreso; XXII LATIN - AMERICAN AND FIRST IBERO-AMERICAN CONGRESS OF PHYSIOLOGICAL SCIENCES; 2006

At the neuromuscular junction, ATP is co-released with Ach, and once in the synaptic space, it is degraded to the presynaptically active metabolite adenosine. How-ever, it was demonstrated that ATP is able to modulate Ach release through a direct effect via it own P2 receptors (R). We found that ATP and the non hydrolysable bg-imido ATP reduced MEPP frequency by 45.3%  and 55.9%. To investigate the type of P2R involved in this action, the effect of bg-imidoATO on MEPP frequency was evaluated on CF1 mouse diaphragms in the presence of different P2 antagonist. Reactive Blue-2 (P2Y4,611,12,13 R antagonist), but not PPADS (P2XR antagonist, although it was also described its action on the P2Y 1,4,6,13R), prevented the effect of the ATP analog (RB  98±2.8% of control values, RB+bg-imido ATP 100.3±4.7%, n:8), suggesting that the effect was mediated by P2YR. On the other hand, pertussis toxin and NEM (blockers of Gi/o protein) , abolished the action of the nucleotide (PTX+bg-imidoATP 102.8±1.6%, n:4; NEM+bg-imidoATP 122.9±5.6%, n:4), indicating that the P2YR involved are coupled to Gi/o protein. Amongst the P2YR, P2Y 12 and  13 are linked to Gi/o protein; tlus, the effect of bg-imido ATP was studied  in the presence of 2MeSAMP and ADC69931MX (P2Y 12/13 antagonists). Both drugs prevented the effect of  bg-imido ATP (2MeSAMP 89± 0.4%, 2MeSAMP+bg-imido ATP  88.5±0.6%   N:4; ARC69931MX     97.0±4.9%,  ARC69931MX+bg-imido  ATP  94.0±3.6%, n:4). More-over  2MeSAMP and ARC69931 MX also antagonized the  presinaptic modulation exerted by 2MeSADP  (53.9±1.6%, n:4), which is the  preferen tial agonist for these subtypes of R (2MeSAMP+2MeSADP 90.8± 1.5%, N:4; ARC69931 MX +2MeSADP 94.6±2.0%,  n:4). The results suggest that P2Y12 or 13 receptors mediate the inhibition of spontaneous Ach secretion induced by adenine nucleotides at mammalian neuromuscular junctions.