Document Detail

Brain opioid receptor density reflects behavioral and heart rate responses in pigs.
MedLine Citation:
PMID:  12126996     Owner:  NLM     Status:  MEDLINE    
Results from our previous research indicate that long-term tether-housed pigs with high and low levels of stereotypies show differences in the density of endogenous opioid receptors in the hippocampus and hypothalamus. It was not clear whether differences in opioid receptor density were induced by the chronic stress of tether housing or stereotypy performance, or were already present before the animals were tethered. The latter possibility was tested in the present experiment. We used a group of 18 nonstereotyping pigs that had no experience with tether housing and investigated whether the animals differed in the density of endogenous opioid receptors in the brain and, if so, whether these differences were related to the animals' reactions to acute challenges. The pigs were subjected to two tests: an open field test and a tethering test. Behavioral reactions as well as heart rate responses were measured. Opioid receptor densities were determined postmortem in the hippocampus and hypothalamus using a membrane binding assay with [(3)H]naloxone as a ligand. Animals differed widely in their responses to the two tests. In support of our hypothesis, we found a relationship between behavioral and heart rate responses and densities of naloxone binding sites in the hippocampus and hypothalamus. The data suggest that endogenous opioid systems in the brain contribute to differences in stress responding between individual pigs.
L W S Loijens; W G P Schouten; P R Wiepkema; V M Wiegant
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Physiology & behavior     Volume:  76     ISSN:  0031-9384     ISO Abbreviation:  Physiol. Behav.     Publication Date:  2002 Aug 
Date Detail:
Created Date:  2002-07-19     Completed Date:  2003-02-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0151504     Medline TA:  Physiol Behav     Country:  United States    
Other Details:
Languages:  eng     Pagination:  579-87     Citation Subset:  IM    
Ethology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, 6700 Wageningen, The Netherlands.
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MeSH Terms
Adaptation, Psychological / physiology
Behavior, Animal / drug effects*
Brain Chemistry / physiology*
Feeding Behavior / physiology
Heart Rate / physiology*
Hippocampus / metabolism
Hypothalamus / metabolism
Motor Activity / physiology
Receptors, Opioid / metabolism,  physiology*
Regression Analysis
Restraint, Physical
Vocalization, Animal / physiology
Reg. No./Substance:
0/Receptors, Opioid

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