Naltrexone, serotonin receptor subtype antagonists, and glucoprivic intake: 1. 2-Deoxy-D-glucose.
Inhibition of deprivation-induced intake by naloxone was significantly enhanced by the 5-hydroxytryptamine3 (5-HT3) antagonist ICS-205,930. Interactions between naloxone and either the general 5-HT antagonist methysergide or the 5-HT2 antagonist ritanserin or ketanserin produced smaller effects. The present study evaluated whether 2-deoxy-D-glucose (2DG, 400 mg/kg) hyperphagia was affected by methysergide (0.5-5 mg/kg), ritanserin (0.25-2.5 mg/kg), or ICS-205,930 (0.5-5 mg/kg) alone or in combination with naltrexone (0.25 and 2.5 mg/kg). Only ICS-205,930 stimulated spontaneous intake for up to 4 h in the light cycle. Only ritanserin (1.25 mg/kg) transiently reduced 2DG hyperphagia. The dose-dependent decreases in 2DG hyperphagia by naltrexone were significantly enhanced by the dose range of ICS-205,930. The inhibition of 2DG hyperphagia by the low naltrexone dose was enhanced by methysergide (5 mg/kg) and ritanserin (1.25 mg/kg). These data suggest that the 5-HT3 receptor primarily interacts with opioid systems to modulate 2DG hyperphagia and that one possible locus of interaction is in the caudal brainstem.
Beczkowska
I W
IW
Department of Psychology and Neuropsychology Doctoral Subprogram Queens College, City University of New York, Flushing 11367.
Koch
J E
JE
Bodnar
R J
RJ
D000818:Animals; D003847:Deoxyglucose / Q000494:pharmacology*; D004435:Eating / Q000187:drug effects*; D005947:Glucose; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D016713:Ritanserin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D000077526:Tropisetron
D007211:Indoles; D007328:Insulin; D012702:Serotonin Antagonists; D016713:Ritanserin; D009271:Naltrexone; D000077526:Tropisetron; D003847:Deoxyglucose; D005947:Glucose; D008784:Methysergide