Inhibition of serotonin synthesis attenuates inhibition of ingestive behavior by CCK-8.
Ingestive behavior was activated in male rats by intraoral infusion of a 1-M solution of sucrose. Injection of cholecystokinin octapeptide (CCK-8; 1.6 or 5.0 micrograms) inhibited ingestion of the sucrose solution and increased the concentration of 5-hydroxytryptamine (5-HT) in the paraventricular hypothalamic nuclei. The inhibitory effect of the low, but not the high, dose of CCK-8 was attenuated by depleting 5-HT in the brain with p-chlorophenylalanine (PCPA; 100 mg/kg for 3 days). Treatment with 5-hydroxytryptophan (20 mg/kg) increased the concentration of 5-HT in the brain of rats pretreated with either NaCl or PCPA and enhanced the inhibitory effect of CCK-8 on ingestive behavior in the PCPA-, but not NaCl-, treated rats. 5-HT may play a role in the mechanism of action of CCK-8 but additional factors must be involved.
Esfahani
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N
Department of Clinical Neuroscience and General Medicine, Karolinska Institute, Huddinge, Sweden.
Bednar
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I
Qureshi
G A
GA
Södersten
P
P
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D004435:Eating / Q000187:drug effects*; D010134:Fenclonine / Q000494:pharmacology; D007267:Injections; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012702:Serotonin Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D012844:Sincalide / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology
D015306:Biogenic Monoamines; D012702:Serotonin Antagonists; D013395:Sucrose; D006916:5-Hydroxytryptophan; D012844:Sincalide; D010134:Fenclonine