Feeding responses to a high dose of 8-OH-DPAT in young and adult rats: influence of food texture.
The present study was undertaken to investigate the hyperphagic responses to the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), in young and adult rats fed either a powder diet or pellets. In the young rats, 8-OH-DPAT (500 micrograms/kg s.c.) increased the consumption of pellets--but not powder--during the 2 h following drug administration. On the other hand, 8-OH-DPAT did not promote hyperphagia in adult rats presented with either pellets or a powdered diet. The influence of the 5-HT1A agonist on midbrain serotonin (5-hydroxytryptamine, 5-HT) turnover was examined. Administration of 8-OH-DPAT (500 micrograms/kg s.c.) induced similar decreases in 5-HT turnover, as reflected by the ratio of 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT, in young and adult rats 1 h after administration. Nevertheless, some metabolic responses to 8-OH-DPAT were found to be influenced by age. Young and adult rats were injected with a low dose of 8-OH-DPAT (50 micrograms/kg s.c.) to specifically test the presynaptic regulation of 5-HT turnover. Again, midbrain 5-HIAA to 5-HT ratios were decreased to the same extent in both young and adult rats. The results suggest that (i) gnawing may be an important parameter in the food consumption that is triggered by a high dose of 8-OH-DPAT, (ii) analysis of the presynaptic effects of 8-OH-DPAT on 5-HT turnover cannot solely explain the influence of the agonist on feeding behavior.
Chaouloff
F
F
Laboratoire de Pharmacologie, INSERM U7, CHU Necker-Enfants Malades, Paris, France.
Serrurrier
B
B
Mérino
D
D
Laude
D
D
Elghozi
J L
JL
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000375:Aging / Q000378:metabolism / Q000523:psychology; D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005247:Feeding Behavior / Q000187:drug effects* / Q000502:physiology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D006963:Hyperphagia / Q000139:chemically induced; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000008:administration & dosage / Q000494:pharmacology*
D001786:Blood Glucose; D009281:Naphthalenes; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin