Activité, Système Moteur & Coordination
Douleur - Allodynie/Hyperalgésie Thermique
Douleur - Spontanée - Déficit de Posture
Douleur - Allodynie/Hyperalgésie Mécanique
Anxiété & Dépression
Apprentissage/Mémoire - Attention - Addiction
Physiologie & Recherche Respiratoire
Métabolisme & Prise Alimentaire
Douleur
Métabolisme
Système moteur
Neurodégénérescence
Thématiques transversales
Système musculaire
Functions de motricité générale
Troubles de l'humeur
Other disorders
Joints
Système Nerveux Central (SNC) 
Système sensoriel
Authors
A. Oliveira, D. Pinhod, A. Albino-Teixeirad, R. Medeirosb, R. J. Dinis-Oliveira et al.
Lab
Faculty of Pharmacy, University of Porto, Porto, Portugal
Journal
Life Sciences
Abstract
Aims
Morphine is extensively metabolized to neurotoxic morphine-3-glucuronide (M3G) and opioid agonist morphine-6-glucuronide (M6G). Due to these different roles, interindividual variability and co-administration of drugs that interfere with metabolism may lead to differences in analgesia. The aim of the study was to investigate the repercussions of administration of an inducer (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) and an inhibitor (ranitidine) of glucuronidation in morphine metabolism and consequent analgesia, using guinea pigs as a suitable model.
Main methods
Thirty male Dunkin–Hartley guinea pigs were divided in six groups: control, morphine, ranitidine, ranitidine + morphine, TCDD and TCDD + morphine. After previous exposure to TCDD and ranitidine, morphine effect was assessed by an increasing temperature hotplate (35–52.5 °C), during 60 min after morphine administration. Then, blood was collected and plasma morphine and metabolites were quantified.
Key findings
Animals treated with TCDD presented faster analgesic effect and 75% reached the cut-off temperature, comparing with only 25% in morphine group. Animals treated with ranitidine presented a significantly lower analgesic effect, compared with morphine group (p ˂ 0.05). Moreover, significant differences between groups were found in M3G levels and M3G/morphine ratio (p ˂ 0.001 and p ˂ 0.0001), with TCDD animals presenting the highest values for M3G, M6G, M3G/morphine and M6G/morphine, and the lowest value for morphine. The opposite was observed in the animals treated with ranitidine.
Significance
Our results indicate that modulation of morphine metabolism may result in variations in metabolite concentrations, leading to different analgesic responses to morphine, in an animal model that may be used to improve morphine effect in clinical practice.
BIOSEB Instruments Used:
Cold Hot Plate Test (BIO-CHP)
