OBJECTIVES: The present study was performed to investigate the discriminative stimulus effects of MG in rats. The pharmacological mechanism of MG action and its derivative, 7-hydroxymitragynine (7-HMG) with a specific focus on opioid receptor involvement was examined in rats trained to discriminate morphine from vehicle. In order to study the dual actions of MG, the effect of cocaine substitution to the MG discriminative stimulus was also performed in MG-trained rats.
METHODS: Male Sprague Dawley rats were trained to discriminate MG from vehicle in a two-lever drug discrimination procedure under a tandem variable-interval (VI 60') fixed-ratio (FR 10) schedule of food reinforcement.
RESULTS: Rats acquired the MG discrimination (15.0 mg/kg, i.p.) which was similar to the acquisition of morphine discrimination (5.0 mg/kg, i.p.) in another group of rats. MG substituted fully to the morphine discriminative stimulus in a dose-dependent manner, suggesting pharmacological similarities between the two drugs. The administration of 7-HMG derivative in 3.0 mg/kg (i.p.) dose engendered full generalisation to the morphine discriminative stimulus. In addition, the MG stimulus also partially generalised to cocaine (10.0 mg/kg, i.p.) stimulus.
CONCLUSION: The present study demonstrates that the discriminative stimulus effect of MG possesses both opioid- and psychostimulant-like subjective effects.
Objectives: This study aimed to determine the specific brain region that is responsive to KOPr treatment following polydrug dependence.
Materials and Methods: The polydrug-dependent mice model was developed using conditioned place preference (CPP) method. Following successful withdrawal phase, the mice were treated with 0.3 mg/kg buprenorphine and 1.0 mg/kg naltrexone. Four brain regions (hippocampus, prefrontal cortex, amygdala, and striatum) were investigated using immunohistochemistry technique. This is to quantify the changes in KOPr expression in each major brain region that was primarily involved in addiction neurocircuits of many substances. Unpaired Student's t test was used to analyze all results, where P < 0.05 is considered significant.
Results: The results showed that treatment with buprenorphine and naltrexone successfully attenuated relapse in 60% of mice (n = 14). A significant upregulation of KOPr was detected in striatum at the end of post-withdrawal phase (P < 0.01, n = 12). This treatment successfully suppressed KOPr in striatum (P < 0.001, n = 12), which supports the positive results seen in the CPP setting. No significant changes were observed in other brain regions studied.
Conclusion: The hyperactivity of striatum suggests that the affected brain region following KOPr antagonist treatment is the region that primarily controls the drug rewarding activity, in which nucleus accumbens is located. This indicates that manipulation of KOPr system is one of the potential targets to treat morphine- or methamphetamine-dependence problem.
Materials and Methods: This cross-sectional study used prescription databases of tertiary hospital settings in Malaysia from 2010 to 2016. Prescriptions for nine NSAIDs (diclofenac, ketoprofen, etoricoxib, celecoxib, ibuprofen, indomethacin, mefenamic acid, meloxicam, and naproxen), tramadol, and five other opioids (morphine, oxycodone, fentanyl, buprenorphine, and dihydrocodeine) prescribed for children aged <18 years were included. Number of annual patients and prescriptions were measured and analyzed using Stata v15.
Results: During a 7-year study period, a total of 5040 analgesic prescriptions of the nine NSAIDs, tramadol, and five other opioids were prescribed for 2460 pediatric patients (81.8% NSAIDs patients, 17.9% tramadol patients, and 0.3% opioid patients). Ibuprofen was the primary analgesic in young children less than 12 years old (≤2 years old [y.o.] [75%], 3-5 y.o. [85%], and 6-12 y.o. [56.3%]). However, there was a wide range of analgesics used in older children (>12 y.o.) with the majority for naproxen (13-15 y.o. (28.2%) and 16-17 y.o. (28.2%). Other frequently prescribed analgesics for older children included ibuprofen (20.6%) and diclofenac (18.2%) for 12-15 y.o. and diclofenac (26.7%) and tramadol (17.6%) for 16-17 y.o.
Conclusion: Ibuprofen was the primary analgesic for children less than 12 y.o., whereas there was a wide range of analgesics prescribed for children age >12 y.o. including naproxen, diclofenac, and tramadol.