[ effect of reversible locus coeruleus [LC] on i.v self-administration of morphine and morphine withdrawal syndrome[MWS] signs in rats]

ABSTRACT

Locus coeruleus [LC] has been hypothesized to play an important role in a variety of behaviors and opiate withdrawal. This study was designed to determine the effects of reversible inactivation of LC on self-administration of morphine and morphine- withdrawal syndrome signs [MWS]. 24 male rats [250-300gr] were surgically implanted bilaterally with cannula in LC then implanted with catheters in the right jugular vein. The rats were tested in 2 groupsControl[saline] and morphine. Morphine group was divided into 3 subgroups control, sham-operated and LC-inactivated group where they received 1microL 2% Lidocaine 5 minutes prior to testing. Animals were allowed to self-administer morphine [1mg/infusion] during 10 consecutive days for 2 hours. The number of lever pressing was recorded. At the end of the training day all groups received naloxone [2mg/kg I.P] and MWS were studied for 30 minutes. LC inactivation prevents the development of tolerance and dependence on morphine and greatly attenuates morphine-withdrawal syndrome. LC inactivation not only attenuates morphine withdrawal syndrome but also prevents morphine tolerance and dependence in rats