• the Korean Society for Brain and Neural Sciences


Original Research Article

Exp Neurobiol 2010; 19(3): 132-139

Published online December 31, 2010

© The Korean Society for Brain and Neural Sciences

5-hydroxy-L-tryptophan Suppressed Food Intake in Rats Despite an Increase in the Arcuate NPY Expression

Young Wha Moon1, Si Ho Choi2, Sang Bae Yoo3, Jong-Ho Lee3 and Jeong Won Jahng3*

1Department of Natural Science, The Catholic University of Korea College of Medicine, Seoul 137-701, Korea, 2Center for Stem Cell and Regenerative Medicine, University of Southern California Keck School of Medicine, Los Angeles 90033, USA, 3Department of Oral and Maxillofacial Surgery, Dental Research Institute, Seoul National University School of Dentistry, Seoul 110-769, Korea

Correspondence to: *To whom correspondence should be addressed.
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This study was conducted to define the underlying mechanism of hypophagia induced by increased central serotonergic action. Rats received 3 daily injections of 5-hydroxy-L-tryptophan (5-HTP), a serotonin precursor, at a dose of 100 mg/kg/10 ml saline at 1 h before lights off. A significant suppression in food intake was observed shortly after the 5-HTP injection and persisted during 3 daily 5-HTP injections. Neuropeptide Y (NPY) expression in the arcuate nucleus increased after 3 days of 5-HTP treatment, as high as in the pair-fed group. Immunoreactivity of phosphorylated extracellular signal-regulated protein kinase (pERK1/2) in the hypothalamic paraventricular nucleus (PVN) was increased markedly by 3 days of 5-HTP treatment, but not by 3 days of pair-fed. mRNA expression levels of serotonin reuptake transporter (5-HTT) was increased in the dorsal raphe nucleus of the 5-HTP treated rats, but not in the pair-fed group. Results suggest that increased pERK1/2 in the PVN of 5-HTP injected rats may be a part of serotonergic anorectic signaling, perhaps blunting the orectic action of NPY; i.e., 5-HTP injected rats showed hypophagia despite of increased NPY expression in the arcuate nucleus.

Keywords: food intake, hypophagia, hypothalamus, serotonin