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Analgesia induced by localized injection of opiate peptides into the brain of infant rats.
MedLine Citation:
PMID:  23203254     Owner:  NLM     Status:  Publisher    
BACKGROUND: Stimulation of a variety of brain sites electrically or by opiates activates descending inhibitory pathways to attenuate noxious input to the spinal cord dorsal horn and produce analgesia. Analgesia induced by electrical stimulation of the periaqueductal grey (PAG) of the midbrain or medial rostral ventral medulla (RVM) matures late, towards the end or past the pre-weaning period. Descending facilitation takes precedence over inhibition. Yet opiates injected intracerebroventricularly or directly into the PAG induce analgesia relatively early in development. Our goal was to re-examine the role of opiates specific to individual receptor types in analgesia at several supraspinal sites. METHODS: Antinociception was tested following microinjection of DAMGO (μ-opiate agonist), DPDPE (∂-opiate agonist) or U50,488 (κ-opiate agonist) into the PAG, RVM or dorsal lateral pons (DLP) in 3-, 10- and 14-day-old rats. RESULTS: DAMGO produced analgesia at 3 days of age at each brain area; the RVM was the most effective and the dorsal PAG was the least effective site. DPDPE produced modest analgesia at 10 and 14 days of age at the ventral PAG, RVM or DLP, but not the dorsal PAG. U50,488H was ineffective at all sites and all ages. CONCLUSIONS: Antinociception could be elicited at all three sites by DAMGO as early as 3 days of age and DPDPE at 10 and 14 days of age. The degree of analgesia increased gradually during the first 2 weeks of life, and likely reflects the maturation of connections within the brain and of descending inhibitory paths from these sites.
G A Barr; S Wang
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-3
Journal Detail:
Title:  European journal of pain (London, England)     Volume:  -     ISSN:  1532-2149     ISO Abbreviation:  Eur J Pain     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9801774     Medline TA:  Eur J Pain     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© 2012 European Federation of International Association for the Study of Pain Chapters.
Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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