title: Long-term effect of morphine administration in young rats on the analgesic opioid response in adult life.
abstract: Neonates, infants and children are often exposed to pain from invasive procedures during intensive care and during the post-operative period. Opioid anesthesia and post-operative opioid analgesia have been used in infants and result in clinical benefits. The objectives of this study were to verify the effect of repeated 5 microg morphine administration (subcutaneous), once a day for 7 days in 8-day-old rats, at P8 until P14. To verify the long-term effect of morphine, the animals were submitted to a second exposure of 5mg/kg (intraperitoneal) of morphine at P80 until P86. Animals that received morphine for 7 days, at P14 did not develop tolerance, however at P80, rats demonstrated greater morphine analgesia. At P86, after 7 days of morphine administration, animals showed classical tolerance. These findings may have important implications for the human neonate, suggesting a possible explanation for the differences in the requirements of morphine observed in the youngest patients.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, UFRGS, 90050-170 Porto Alegre, RS, Brazil.
authors.forename: Joanna Ripoll
authors.initials: JR
authors.lastname: Rozisky
authors.forename: Giovana
authors.initials: G
authors.lastname: Dantas
authors.forename: Lauren Spezia
authors.initials: LS
authors.lastname: Adachi
authors.forename: Viviane Soares
authors.initials: VS
authors.lastname: Alves
authors.forename: Maria Beatriz Cardoso
authors.initials: MB
authors.lastname: Ferreira
authors.forename: João José Freitas
authors.initials: JJ
authors.lastname: Sarkis
authors.forename: Iraci Lucena Da Silva
authors.initials: IL
authors.lastname: Torres
mesh_terms: D000367:Age Factors; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects; D004334:Drug Administration Schedule; D004361:Drug Tolerance / Q000502:physiology; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine