Pain is one of the most common forms of psychological stress and the most common phenomenon in medical science. analgesics such as alpha-2 adrenoceptor agonists, which have low risk of complications, can be effective in relieve pain. locus coeruleus (lc) of the brainstem nor-epinephrine (ne) system have a key role in the mechanisms of the pain modulation. former studies demonstrate that potassium channels represent an important step in the transduction mechanism underlying central antinociception induced by activation of alpha-2adrenoceptors.
Methods
This study was performed on 56 male wistar rats weighing 250-300 g that were divide into six groups of eight rats. dexmedetomidine ( 3.5 μg/kg) was used as an agonist for alpha-2 adrenergic receptors and 5μg/kg of yohimbine (an antagonist for these receptors) was used to investigate the role of alpha-2 adrenergic receptors in analgesia. iberiotoxin at a dose of 400 nm was also injected into locus coeruleus. normal saline was applied as solvents. pain severity was evaluated using formalin test at a concentration of 2%.
Results
One-way anova analysis of chronic pain showed that dexmedetomidine can reduce chronic pain behavior scores significantly. moreover, 5 μg/kg administration of yohimbine could significantly inhibit analgesic effect of dexmedetomidine. injection of iberiotoxin at a dose of 400 nm significantly diminished analgesic effects of dexmedetomidine.
Conclusion
Alpha-2 adrenergic receptor agonists could induce analgesia (chronic pain), and the antagonist of this receptor inhibited the analgesic effect of agonists of these receptors. bk channel blocker prevented analgesic effect of adrenergic receptor agonists, as well.
Keywords
Alpha-2adrenoceptors, bk channel, locus coeruleus, pain
