Biological profile and bioavailability of imidazoline compounds on morphine tolerance modulation
作者:Giovanni Caprioli、Valerio Mammoli、Massimo Ricciutelli、Gianni Sagratini、Massimo Ubaldi、Esi Domi、Laura Mennuni、Chiara Sabatini、Chiara Galimberti、Flora Ferrari、Chiara Milia、Eleonora Comi、Marco Lanza、Mario Giannella、Maria Pigini、Fabio Del Bello
DOI:10.1016/j.ejphar.2015.11.021
日期:2015.12
Tolerance to opioid administration represents a serious medical alert in different chronic conditions. This study compares the effects of the imidazoline compounds 1,2, and 3 on morphine tolerance in an animal model of inflammatory pain in the rat. 1,2, and 3 have been selected in that, although bearing a common scaffold, preferentially bind to alpha(2)-adrenoceptors, imidazoline 12 receptors, or both systems, respectively. Such compounds have been tested in vivo by measuring the paw withdrawal threshold to mechanical pressure after complete Freund's adjuvant injection. To determine the ligand levels in rat plasma, an HPLC-mass spectrometry method has been developed. All the compounds significantly reduced the induction of morphine tolerance, showing different potency and duration of action. Indeed, the selective imidazoline I-2 receptor interaction (2) restored the analgesic response by maintaining the same timedependent profile observed after a single morphine administration. Differently, the selective alpha(2c)-adrenoceptor activation (1) or the combination between alpha(2c)-adrenoceptor activation and imidazoline I-2 receptor engagement (3) promoted a change in the temporal profile of morphine analgesia by maintaining a mild but long lasting analgesic effect. Interestingly, the kinetics of compounds in rat plasma supported the pharmacodynamic data. Therefore, this study highlights that both peculiar biological profile and bioavailability of such ligands complement each other to modulate the reduction of morphine tolerance. Based on these observations, 1-3 can be considered useful leads in the design of new drugs able to turn off the undesired tolerance induced by opioids. (C) 2015 Elsevier B.V. All rights reserved.