Beta-adrenergic receptor blockers effects on the antinociceptive action of imipramine against thermal induced pain in albino mice

• Main Authors: H A Zawia, F A Blaou, A S Elhwuegi
• Format: Article
• Language: Arabic
• Published: Wolters Kluwer Medknow Publications 2016-01-01
• Series: Libyan International Medical University Journal
• Subjects: Imipramine; atenolol; propranolol; analgesia; thermal nociception
• Online Access: http://journal.limu.edu.ly/article.asp?issn=2519-139x;year=2016;volume=1;issue=1;spage=17;epage=26;aulast=Zawia;type=0
• ISSN: 2519-139X; 2519-139X

Introduction: Tricyclic antidepressant have been shown to be effective in treatment of pain of varying etiology, monoaminergic system seems to be implicated in this phenomena. This research examines the role of beta-adrenergic receptor blockers on the antinociceptive effect of imipramine in albino mice using thermal model of pain. Methods: Different groups of five animals each were injected intraperitoneal by different doses of imipramine only (2.5, 7.5,15, 30 mg/kg), atenolol (2 mg/kg), propranolol (6mg/kg), or the combination of the different doses of imipramine with the fixed dose of atenolol or propranolol. The degree of analgesia was measured as an increase in reaction time to pain in the hot plate one hour after drugs injections. Results: Imipramine produced dose dependent increase in reaction time from 129% with the lowest dose to 196% with the highest dose. One-way ANOVA analysis has shown that the addition of a fixed dose of propranolol antagonized significantly the increase in reaction time to 75% with the lowest dose and 118.9% with the highest dose of imipramine. On the other hand, atenolol failed to antagonize significantly the increase in reaction time induced by imipramine. Conclusion: Imipramine has a significant analgesic effect on albino mice in the hot plate test. The antinociceptive action of imipramine seems to be of central origin and possibly mediated, at least in part, by beta adrenergic receptors, as this analgesic effect can be blocked by propranolol, a centrally acting non-selective beta adrenergic receptor antagonist, but not with atenolol which blocks only the peripheral beta receptors.