In this study, the effect of reversible inactivation of locus ceruleus (LC) on naloxone- induced withdrawal syndrome in paragigantocellular (PGi) neurons in morphine- dependent rats was investigated. For inactivation of LC, 1 µl of lidocaine (2%) was used and for induction of withdrawal syndrome, naloxone hydrochloride (2 mg/kg) was injected systemically. The results showed that in dependent group with intact LC, PGi single unit activity increased following naloxone administration, whereas in dependent group with inactivated LC, the observed increase was not significant.

Keywords: Paragigantocellular nucleus; Locus ceruleus; Morphine dependence; Withdrawal syndrome; Functional inactivation