RESUMO
Some reports show that co-administration of Matricaria chamomilla [MC] extract with morphine, greatly attenuate the development of morphine dependence and inhibit the expression of abstinence syndrome in morphine-dependent animals. Locus Coeruleus [LC] and nucleus paragigantocellularis [PGi] play an important role in developing symptoms of opiate withdrawal. The objective of this study was to determine the effects of Matricaria chamomilla extract infusion into PGi on morphine withdrawal syndrome signs [MWS] of rats. Thirty male rats [weight: 250-300gr] were surgically implanted with cannula at the PGi and then tested in 2groups: saline [control group] and morphine [twice daily for 7 days]. The dose of morphine on the first and second days was 2.5 mg/kg and was doubled every day. On 7[th] day, the animals received the last injection of morphine [50mg/kg] and divided in 4 subgroups: the morphine group [which only received morphine] and three MC groups [which received 1 micro l of MC extract with the concentrations of 10, 25, 50 micro g/micro l, 5 min before naloxone administration]. In the end of the training day [7[th] day] all groups were received naloxone [5mg/kg IP] 3h after last injection of morphine and then the frequencies of withdrawal behavior [jumping, climbing] were assessed for 30 minute. Our results showed that central administration of MC extract, especially at high doses [25 micro g/micro l], significantly attenuates most signs of the morphine withdrawal syndrome. These results suggest that the injection of MC extract into the PGi may be helpful for morphine withdrawal syndrome treatment