N-substitution and á1-adrenergic receptor affinity of laudanosine analogues

• PATRICIO ITURRIAGA-VÁSQUEZ ^[3] ; BRUCE K CASSELS ^[3] ; M. DOLORES IVORRA ^[1] ; M. PILAR D'OCON ^[2]
  1. [1] Universidad de Chile

     Universidad de Chile

     Santiago, Chile

     
  2. [2] Universitat de València

     Universitat de València

     Valencia, España

     
  3. [3] Universidad de Chile Millennium Institute for Advanced Research in Cell Biology and Biotechnology

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• Localización: Journal of the Chilean Chemical Society (Boletín de la Sociedad Chilena de Química), ISSN-e 0717-6309, ISSN 0366-1644, Vol. 51, Nº. 3, 2006, págs. 935-937
• Idioma: inglés
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  • Benzyltetrahydroisoquinoline (BTHIQ) molecules are able to adopt widely differing conformations that depend on the presence or absence of N-substituents. To assess the possible role of BTHIQ conformation on the affinity of these compounds for a 1-adrenergic receptors, of interest for the management of hypertension, the racemic N-unsubstituted BTHIQ norlaudanosine and a series of N-alkylated derivatives were assessed for binding to rat brain cortical sites labelled with the radioligand [³H]prazosin. The a 1-adrenergic affinity in this series increased with the bulk of the substituent on the nitrogen atom, from the N-ethyl to the N-propyl analogue. Comparison of these results with published data for related BTHIQs and for the rigid mimics of the fully extended and semi-folded conformations of laudanosine, tetrahydropalmatine and glaucine, suggested that the a 1-adrenergic receptor binding site is able to accommodate either conformation. The presence of a bulky substituent on the nitrogen atom seems to favor receptor binding independently of the favored conformation, and that the orientation in which BTHIQs are bound probably differs depending on the presence or absence of a hydroxyl group at a key position