Document Detail

Role of diurnal variation and receptor specificity in the opioidergic regulation of food intake in free-fed and food-deprived rats.
MedLine Citation:
PMID:  1654568     Owner:  NLM     Status:  MEDLINE    
The effects of opioid agonists, morphine (MOR) and ketocyclazocine (KCZ), and antagonists, naltrexone (NALTX) and Mr2266, were investigated on food intake under various conditions, i.e., during light and dark phases of diurnal cycle and free-fed and fasting states in rats. NALTX showed a greater anorexic effect during dark phase, whereas Mr2266 produced such effect during light phase. This suggests that mu-receptors play a major role during dark phase while kappa-receptors are more important in light phase. The comparison of effects of different opioidergic drugs in fasted and free-fed rats showed that NALTX and Mr2266 reduced the elevated basal food intake in 18-h fasted rats to free-fed control levels. Therefore, it appears that enhanced endogenous mu- and kappa-directed neural mechanisms are one of the factors responsible for enhancing food intake in fasted rats. Differential role of MOR and KCZ on food intake in free-fed and fasted rats is also indicated in our study. Both agonists produced a biphasic response in fasted rats, i.e., hyperphagia (0-1 h) followed by hypophagia (1-6 h). However, a generalized hyperphagic effect is observed in free-fed rats (except during 3-6 h by MOR). The initial hyperphagic effect is more prominent in fasted rats which may be due to additive effects of endopioid mechanisms. Specificity of the response at various intervals is confirmed by blockade with NALTX and Mr2266. NALTX appears more potent than Mr2266 in antagonising the effects of MOR but markedly less potent than Mr2266 in inhibiting the effects of KCZ. This suggests that both MOR and KCZ have a mu as well as kappa component in food intake response.
K Gulati; A Ray; K K Sharma
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Physiology & behavior     Volume:  49     ISSN:  0031-9384     ISO Abbreviation:  Physiol. Behav.     Publication Date:  1991 Jun 
Date Detail:
Created Date:  1991-10-23     Completed Date:  1991-10-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0151504     Medline TA:  Physiol Behav     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1065-71     Citation Subset:  IM    
Department of Pharmacology, University College of Medical Sciences & GTB Hospital Shahdara, Delhi, India.
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MeSH Terms
Circadian Rhythm / physiology*
Endorphins / physiology*
Feeding Behavior / physiology*
Hunger / physiology*
Rats, Inbred Strains
Receptors, Opioid / physiology*
Receptors, Opioid, kappa
Receptors, Opioid, mu
Satiety Response / physiology
Reg. No./Substance:
0/Endorphins; 0/Receptors, Opioid; 0/Receptors, Opioid, kappa; 0/Receptors, Opioid, mu
Erratum In:
Physiol Behav 1993 Sep;54(3):613

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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