The effects of repeated administration of morphine and methadone, followed by a challenge dose of either morphine or methadone were examined ex vivo in rat frontal cortical slices that were prepared 1 h after final drug administration. Morphine challenge dose (5 mg/kg), administered 14 days after the end of repeated morphine pretreatment (10 mg/kg, administered 7 times) decreased both the AMPA/...

BACKGROUND The feasibility and clinical implication of drug monitoring of morphine, morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G) need further investigation. This study aimed to determine what predicts serum concentrations of morphine in cancer patients receiving continuously intravenous morphine, the relationships between serum concentration of morphine/its metabolites and urin...

BACKGROUND/PURPOSE We previously showed that subsequent intrathecal (i.t.) injection of resveratrol (30 μg) significantly reverses morphine-evoked neuroinflammation in morphine-tolerant rats. The present study examined the underlying mechanism. METHODS Male Wistar rats were implanted with two i.t. catheters, one of which was connected to a miniosmotic pump and used for morphine (15 μg/h) or s...

Chloramphenicol, an in vitro inhibitor of the glucuronidation of morphine to its putative antianalgesic metabolite, morphine-3-glucuronide (M3G), was coadministered with morphine in adult male Sprague-Dawley rats to determine whether it inhibited the in vivo metabolism of morphine to M3G, thereby enhancing morphine antinociception and/or delaying the development of antinociceptive tolerance. Pa...

Laboratory data indicate that morphine decreases the numbier of peritoneal and alveolar macrophages (Mphi) and compromises their phagocytic capability for immune complexes and bacteria. We hypothesize that morphine decreases the number of, as well as compromises the phagocytic capability of, Mphi by programming their death. We studied the effect of morphine on Mphi apoptosis in vivo as well as ...

Deep brain stimulation (DBS) of the nucleus accumbens (NAc) is a potential remedial therapy for drug craving and relapse, but the mechanism is poorly understood. We investigated changes in neurotransmitter levels during high frequency stimulation (HFS) of the unilateral NAc on morphine-induced rats. Sixty adult Wistar rats were randomized into five groups: the control group (administration of s...

Glycyl-glutamine (Gly-Gln; beta-endorphin(30-31)) is an endogenous dipeptide synthesized from beta-endorphin(1-31). Previous investigations have shown that Gly-Gln inhibits the cardiovascular and respiratory depression caused by morphine and beta-endorphin(1-31), but it does not interfere with opioid analgesia. In this study, we tested whether Gly-Gln administration would influence morphine-ind...

Morphine, morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), and 6-monoacetylmorphine (6-MAM) were isolated from body fluids using solid-phase extraction and determined by means of atmospheric pressure chemical ionization-mass spectrometry-liquid chromatography (APCI-LC-MS) in selected ion monitoring mode. The following ions were monitored: m/z 286 for morphine; m/z 286 and 462 for M3G...

BACKGROUND After cardiac surgery adequate postoperative analgesia is necessary. We assessed analgesia using intrathecal morphine and clonidine. METHODS In a double-blind randomized study, 45 patients having coronary artery bypass graft surgery were allocated randomly to receive i.v. patient-controlled analgesia (PCA) morphine (bolus, 1 mg; lock-out interval, 7 min) (control group), either alo...

When rats are forced to drink a morphine solution as their only source of fluid, they eventually reverse their initial preference and drink more morphine than water in a two-bottle preference test. The cause of this shift in preference was examined with the taste reactivity test which involves the analysis of fixed action patterns elicited by taste solutions infused into rats' mouths. Three mor...