Browsing by Author "Chrestia, Juan Facundo"

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    Side Groups Convert the α7 Nicotinic Receptor Agonist Ether Quinuclidine into a Type I Positive Allosteric Modulator
    (2023) Viscarra, Franco; Chrestia, Juan Facundo; Sanchez, Yaima; Perez, Edwin G.; Biggin, Philip C.; Bouzat, Cecilia; Bermudez, Isabel; Lopez, Jhon J.
    The quinuclidine scaffold has been extensively used forthe developmentof nicotinic acetylcholine receptor (nAChR) agonists, with hydrophobicsubstituents at position 3 of the quinuclidine framework providingselectivity for & alpha;7 nAChRs. In this study, six new ligands (4-9) containing a 3-(pyridin-3-yloxy)quinuclidinemoiety (ether quinuclidine) were synthesized to gain a better understandingof the structural-functional properties of ether quinuclidines.To evaluate the pharmacological activity of these ligands, two-electrodevoltage-clamp and single-channel recordings were performed. Only ligand 4 activated & alpha;7 nAChR. Ligands 5 and 7 had no effects on & alpha;7 nAChR, but ligands 6, 8, and 9 potentiated the currents evokedby ACh. Ligand 6 was the most potent and efficaciousof the potentiating ligands, with an estimated EC50 forpotentiation of 12.6 & PLUSMN; 3.32 & mu;M and a maximal potentiationof EC20 ACh responses of 850 & PLUSMN; 120%. Ligand 6 increased the maximal ACh responses without changing thekinetics of the current responses. At the single-channel level, thepotentiation exerted by ligand 6 was evidenced in thelow micromolar concentration range by the appearance of prolongedbursts of channel openings. Furthermore, computational studies revealedthe preference of ligand 6 for an intersubunit site inthe transmembrane domain and highlighted some putative key interactionsthat explain the different profiles of the synthesized ligands. Notably,Met276 in the 15 & PRIME; position of the transmembrane domain 2 almostabolished the effects of ligand 6 when mutated to Leu.We conclude that ligand 6 is a novel type I positiveallosteric modulator (PAM-I) of & alpha;7 nAChR.