Naloxone and serotonin receptor subtype antagonists: interactive effects upon deprivation-induced intake.
Whereas opiate receptor antagonists generally act to inhibit food intake under a variety of physiological conditions in rats, agonists of some serotonin (5-HT) receptor subtypes appear to stimulate intake, and others appear to inhibit intake. The present study evaluated the effects of the general 5-HT receptor antagonist, methysergide (1-5 mg/kg), the 5-HT2 receptor antagonists, ketanserin (1-2.5 mg/kg) and ritanserin (1-2.5 mg/kg), and the 5-HT3 receptor antagonist, ICS 205930 (1-5 mg/kg) upon deprivation (24 h)-induced intake themselves, and upon the hypophagic properties of the general opiate receptor antagonist, naloxone (1-5 mg/kg). Whereas the high doses of methysergide (0.5-4 h, 34%) and ketanserin (0.5 h, 28%) significantly decreased deprivation-induced intake themselves, ritanserin and ICS 205930 were without effect. Naloxone produced dose-dependent reductions in deprivation-induced intake (24-45%). Methysergide (1 mg/kg) significantly potentiated naloxone (5 mg/kg) hypophagia after 0.5 h. Significant potentiations of hypophagia occurred following pairing the 1 mg/kg ketanserin dose with the 1 and 5 mg/kg naloxone doses at 2 and 4 h respectively, and pairing the 2.5 mg/kg ketanserin and 1 mg/kg naloxone doses at 0.5 and 2 h. Whereas the 1 mg/kg dose of ritanserin eliminated naloxone (1 mg/kg) hypophagia over a 2-h time course, ritanserin failed to exert further effects in other dose conditions. The differences between ketanserin and ritanserin in their effects upon deprivation-induced feeding and naloxone hypophagia suggest that the former's antagonistic actions upon alpha-adrenergic receptors may be responsible for its effects.(ABSTRACT TRUNCATED AT 250 WORDS)
Beczkowska
I W
IW
Department of Psychology, Queens College, CUNY Flushing 11367.
Bodnar
R J
RJ
D000818:Animals; D004347:Drug Interactions; D005247:Feeding Behavior / Q000187:drug effects*; D005508:Food Deprivation / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D016713:Ritanserin; D012702:Serotonin Antagonists; D000077526:Tropisetron
D007211:Indoles; D010880:Piperidines; D012702:Serotonin Antagonists; D016713:Ritanserin; D009270:Naloxone; D000077526:Tropisetron; D007650:Ketanserin; D008784:Methysergide