Document Detail

Facilitatory effects of opioids on the discharges of visceral nociceptors.
MedLine Citation:
PMID:  2573404     Owner:  NLM     Status:  MEDLINE    
Effects of opioids on the activity of visceral nociceptors were tested using the in vitro testis-spermatic nerve preparations excised from deeply anesthetized dogs. Morphine, DADLE and dynorphin (10 microM) elicited discharges of polymodal receptors in approximately 1/3 of the tested cases. The incidence of the excitatory response of morphine increased at higher concentrations. The excitatory responses were quite variable among preparations and showed a strong tendency for tachyphylaxis. Similar increases in discharges were elicited when morphine was applied during the steady state of the response evoked by bradykinin (BK) or BK mixed with prostaglandin E2. Pretreatment of morphine for 5 min significantly augmented the subsequent BK responses for 30 min or more. Naloxone per se induced neither excitation nor augmentation of the subsequent BK response, however it reversed the augmenting effect of morphine on BK response. In contrast with previous reports proposing peripheral analgesic effects of opioids, suppressive effects on nociceptors were never observed in the present experiment. Peripheral effects of opioids were discussed.
T Kumazawa; K Mizumura; J Sato; M Minagawa
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Brain research     Volume:  497     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  1989 Sep 
Date Detail:
Created Date:  1990-01-11     Completed Date:  1990-01-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  231-8     Citation Subset:  IM    
Department of Nervous and Sensory Functions, Nagoya University, Japan.
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MeSH Terms
Bradykinin / pharmacology
Dinoprostone / pharmacology
Dynorphins / pharmacology*
Enkephalin, Leucine / analogs & derivatives*,  pharmacology
Enkephalin, Leucine-2-Alanine
Epididymis / innervation
Evoked Potentials / drug effects
Morphine / pharmacology*
Naloxone / pharmacology
Nociceptors / drug effects,  physiology*
Testis / innervation*
Reg. No./Substance:
363-24-6/Dinoprostone; 465-65-6/Naloxone; 57-27-2/Morphine; 58-82-2/Bradykinin; 58822-25-6/Enkephalin, Leucine; 63631-40-3/Enkephalin, Leucine-2-Alanine; 74913-18-1/Dynorphins

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