RESUMEN
cis-N-Substituted N-normetazocine enantiomers possess peculiar pharmacological profiles. Indeed, dextro enantiomers bind with high affinity σ1 receptor while opposite enantiomers bind opioid receptors. In spite of their stereochemistry, cis-N-2-phenylethyl N-normetazocine (phenazocine) enantiomers showed mixed opioid/σ1 receptor profiles and a significant in vivo analgesia. To the best of our knowledge, there is no information available regarding the evaluation of σ1 pharmacological profile in the antinociceptive effects of (+)- and (-)-phenazocine. Therefore, the present study was designed to ascertain this component by in vitro and in vivo studies. In particular, we tested the σ1 affinity of both enantiomers by a predictive binding assay in absence or presence of phenytoin (DPH). Our results showed that DPH (1 mM) did not increase the σ1 receptor affinity of (+)-and (-)-phenazocine (Ki = 3.8 ± 0.4 nM, Ki = 85 ± 2.0 nM, respectively) suggesting a σ1 antagonist profile of both enantiomers. This σ1 antagonistic component of two phenazocine enantiomers was corroborated by in vivo studies in which the selective σ1 receptor agonist PRE-084, was able to unmask their σ1 antagonistic component associated with the opioid activity. The σ1 antagonistic component of (+)- and (-)-phenazocine may justify their analgesic activity and it suggests that they may constitute useful lead compounds to develop new ligands with this dual activity.
Asunto(s)
Antagonistas de Narcóticos/síntesis química , Antagonistas de Narcóticos/farmacología , Fenazocina/síntesis química , Fenazocina/farmacología , Receptores Opioides/agonistas , Analgésicos/síntesis química , Analgésicos/química , Analgésicos/farmacología , Animales , Sitios de Unión , Ratones , Estructura Molecular , Morfolinas/química , Morfolinas/farmacología , Antagonistas de Narcóticos/química , Dolor/tratamiento farmacológico , Dimensión del Dolor , Fenazocina/química , Unión Proteica/efectos de los fármacos , EstereoisomerismoRESUMEN
Two novel 8-azabicyclo[3.2.1]octan-3-ol derivatives, 11a and 11b, with high affinity for sigma-2 receptors and a very good sigma-1/sigma-2 selectivity ratio were synthesized. In comparison with several well established sigma-2 selective ligands, 11 b showed a very low sigma-1 receptor affinity. Functional assays demonstrated that 11b acts as an agonist and in A-375 human melanoma cell line is able to lower levels of procaspase-3, thus confirming a potential major role for sigma-2 pure agonists in the treatment of rapid proliferating melanoma cells.
