Long-term consumption of sugar-rich diet decreases the effectiveness of somatodendritic serotonin-1A receptors.
8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), a 5-hydroxytryptamine (5-HT)-1A selective agonist was used to investigate a possible role of somatodendritic serotonin-1A receptors in the precipitation of hyperphagia and decreases of 5-HT metabolism associated with long-term consumption of sugar rich-diet. In the first part of study, dose-related hyperphagic effects of 8-OH-DPAT were monitored in freely feeding rats. In the second part of study, rats were fed freely on a sugar-rich diet (prepared by mixing standard rodent diet with table sugar in the ratio of 3:1 [w/w]) for 5 weeks. Hyperphagic effects of 8-OH-DPAT were monitored in sugar-rich diet and normal diet treated rats by injecting the drug at a dose of 0.25 mg/kg body weight, a dose that produced significant hyperphagia. Effects of 8-OH-DPAT on decreasing 5-HT metabolism in the hypothalamus were also investigated in the two groups. Results showed that administration of 8-OH-DPAT at a dose of 0.25 mg/kg body weight elicited hyperphagia and decreased 5-HT metabolism in normal diet treated animals but the effects in sugar-rich diet treated animals were smaller and not significant suggesting a decrease in the effectiveness of somatodendritic 5-HT-1A receptors, which provide a feedback control over the synthesis and release of 5-HT in terminal region. A possible mechanism involved in sugar-diet induced decreases of 5-HT metabolism is discussed.
Inam
Qurrat-ul-Aen
QU
Neurochemistry and Biochemical Neuropharmacology Research Unit, Department of Biochemistry, University of Karachi, Karachi, Pakistan. qurrat_biochemist@yahoo.com
Jabeen
Bushra
B
Haleem
M A
MA
Haleem
Darakhshan J
DJ
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage; D000818:Animals; D019422:Dietary Sucrose / Q000008:administration & dosage / Q000009:adverse effects*; D004435:Eating / Q000187:drug effects; D025461:Feedback, Physiological; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D006963:Hyperphagia / Q000209:etiology* / Q000503:physiopathology; D007031:Hypothalamus / Q000737:chemistry / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D044282:Receptor, Serotonin, 5-HT1A / Q000502:physiology*; D012701:Serotonin / Q000032:analysis / Q000378:metabolism*; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage; D014364:Tryptophan / Q000032:analysis
D019422:Dietary Sucrose; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D014364:Tryptophan