Abstract/Details

The effects of chronic naltrexone treatment on lateral hypothalamic self-stimulation, stimulation-escape, and stimulation-induced feeding


1990 1990

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Abstract (summary)

This work investigates the role of endogenous opioids in three behaviors induced by lateral hypothalamic (LH) stimulation: reward, escape and feeding.

Studies addressing the issue of whether LH stimulation reward is mediated by endogenous opioids have thus far failed to produce conclusive results. These studies, using the broad-spectrum opioid receptor antagonists naloxone (NAL) and naltrexone (NTX), have invariably suffered from high between-subjects variability. We report a set of experiments that elucidate the nature of this variability using opioid receptor unregulation and supersensitivity to endogenous opioid peptides induced by chronic NTX treatment.

Results indicate that electrode placement within the LH, a previously uncontrolled variable, determines the extent to which LH self-stimulation (SS) is mediated by opioid mechanisms. Following chronic NTX treatment, SS is potentiated only at electrode placements that do not support stimulation-escape (SE); these placements lie caudally within the LH. At rostrally located electrodes that do support SE, neither SS nor SE are altered. An ancillary experiment using acute NTX showed a similar dependence of NTX effects on electrode placement and suggested the presence of an opioid mechanism inhibitory to reward. This mechanism appears to be activated only by stimulation at mid-hypothalamic (tuberal) levels.

Past studies have shown that LH stimulation-induced feeding (SIF) is clearly mediated by endogenous opioids since it is inhibited by systematically applied NAL and NTX, and facilitated by systematically applied opioid agonists. However, consequent to chronic NTX treatment, we observed an increase in SIF thresholds relative to baseline levels. It is proposed that this response is effected at the periaqueductal gray or peripherally, since opioid agonists acting locally within these regions disrupt LH SIF. Our findings suggest that there exists an opioid mechanism that is inhibitory to feeding.

Indexing (details)


Subject
Physiological psychology;
Psychobiology;
Psychology;
Experiments
Classification
0989: Physiological psychology
0349: Psychobiology
0623: Psychology
0623: Experiments
Identifier / keyword
Psychology
Title
The effects of chronic naltrexone treatment on lateral hypothalamic self-stimulation, stimulation-escape, and stimulation-induced feeding
Author
Uysal, Suzan
Number of pages
170
Publication year
1990
Degree date
1990
School code
0146
Source
DAI-B 51/12, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Coons, Edgar E.
University/institution
New York University
University location
United States -- New York
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9113061
ProQuest document ID
303870646
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/303870646
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