ALTERATION IN OREXIN TYPE ONE RECEPTOR EXPRESSION FOLLOWING OPIATE DEPENDENCY IN RATS LOCUS COERULEUS NUCLEUS

Background and Aim : Repetitive administration of opioid agonists is associated with the induction of dependency to the effects of these substances and thus limits their application. The locus coeruleus (LC) is a key brain structure implicated in dependency, tolerance and the expression of somatic signs of morphine withdrawal syndrome. Orexin (also known as hypocretin) is involved in morphine tolerance and dependence and it’s type 1 receptor (OXR1) has been detected in LC nucleus. We studied alteration of OXR1 in LC neurons of morphine dependent rats. Methods : Male Wistar rats weighing 250-300 g were used in this study, in 3 groups as control, saline treated and morphine treated rats. To incite dependency, morphine sulfate was injected subcutaneously (10 mg/kg, i.p.) twice a day (every 12 h) for 10 days. In this study we used RT-PCR in order to measure the expression of orexin 1 receptor in LC neurons.Results : Morphine injection during 10 days led to the induction of morphine dependency in LC neurons which was observed as a significant increase in behavioral withdrawal syndrome following naloxone injection. Chronic administration of morphine caused an increase in OXR1 expression in neurons of LC but in control and saline treated rats no significant change was observedConclusion : The increased expression of the orexin type 1 receptors during dependence indicated that orexin receptors are involved in inducing dependency. another possible hypothesis for this alteration express that this expression amplification may occur because morphine tolerance

کلیدواژه ها:

Opioids ، dependency ، Locus coeruleus nucleus ، Orexin ، RT-PCR