Exp Neurobiol.  2010 Dec;19(3):132-139. 10.5607/en.2010.19.3.132.

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

• Moon YW
• Choi SH
• Yoo SB
• Lee JH
• Jahng JW

• KMID: 1460757
• DOI: http://doi.org/10.5607/en.2010.19.3.132

Abstract

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.

Keyword

food intake; hypophagia; hypothalamus; serotonin

MeSH Terms

5-Hydroxytryptophan
Animals
Arcuate Nucleus
Eating
Hypothalamus
Light
Neuropeptide Y
Paraventricular Hypothalamic Nucleus
Protein Kinases
Raphe Nuclei
Rats
RNA, Messenger
Serotonin
5-Hydroxytryptophan
Neuropeptide Y
Protein Kinases
RNA, Messenger
Serotonin