Linked Life Data

6302245

Source:http://linkedlifedata.com/resource/pubmed/id/6302245

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1983-6-17
pubmed:abstractText
The rate and degree of tolerance development of morphine, normorphine and methadone were assessed in vitro on the guinea-pig ileum. After the half-maximal concentration to inhibit electrically induced contractions (IC50) for each compound was determined, tolerance to a fixed concentration representing 0.5, 1 or 2 times its IC50 was induced by incubation at 37 degrees C for 1, 2 or 4 hr. The IC50 was then redetermined and the ratio of the IC50 after and before incubation provided a quantitative index of the degree of tolerance development to each agonist. For any given concentration or time, morphine induced the highest, whereas normorphine the intermediate and methadone the lowest degree of tolerance. Tolerance to opiates was associated with some degree of physical dependence as evidenced by the fact that the application of naloxone at the end of each experiment elicited a muscular contraction. Specificity of tolerance development to opiates was demonstrated by several experiments. Coincubation of morphine with naloxone under the same conditions resulted in an inhibition of tolerance development. The stereospecificity of the process was demonstrated by the fact that levorphanol and I-methadone induced a high degree of tolerance, whereas, under the same conditions the less active d-isomers, dextrorphan and d-methadone, did not. Moreover, subsensitivity to acetylcholine, norepinephrine and adenosine monophosphate did not develop in the presence of tolerance to morphine. The validity of this method for investigating mechanisms involved in tolerance and physical dependence was further demonstrated by obtaining data compatible with earlier experiments in vivo that cyclic AMP enhances tolerance development and cycloheximide inhibits this phenomenon. The present method should facilitate studies on the mechanisms involved in opiate tolerance and physical dependence development.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0022-3565
pubmed:author
pubmed:issnType
Print
pubmed:volume
225
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
251-5
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1983
pubmed:articleTitle
A rapid and simple method for the quantitative determination of tolerance development to opiates in the guinea-pig ileum in vitro.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.