Systemic 5-hydroxy-L-tryptophan down-regulates the arcuate CART mRNA level in rats.
This study was conducted to determine if serotonin (5-hydroxytryptamine; 5-HT) system correlates with the hypothalamic expression of cocaine-amphetamine-regulated transcript (CART) gene. Rats received intraperitoneal 5-hydroxy-L-tryptophan (5-HTP; a single or three daily injections at a dose of 100 mg/kg/10 ml), and CART mRNA level in the hypothalamus was examined by in situ hybridization at different time points. The 5-HT contents of the hypothalamus as well as the brainstem was increased persistently by 5-HTP injections, and food intake and body weight gain reduced. CART mRNA level decreased significantly in the hypothalamic arcuate nucleus by three daily 5-HTP, but not by a single injection. The pair-fed group of the chronic 5-HTP did not show a decrease in the arcuate CART mRNA level. The plasma leptin level markedly decreased in the chronic 5-HTP group, compared to the saline group, however, still higher than the pair-fed group with a statistical significance. These results suggest that 5-HT may suppress CART mRNA expression in the arcuate nucleus, not only by leptin signaling via its anorectic effect on the control of food intake, but also by some non-leptin mediated pathway.
Choi
Si Ho
SH
Department of Pharmacology and Yonsei Brain Research Institute, BK21 Project for Medical Science, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
Kwon
Bum Sup
BS
Lee
Seoul
S
Houpt
Thomas A
TA
Lee
Hoon Taek
HT
Kim
Dong Goo
DG
Jahng
Jeong Won
JW
D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D001933:Brain Stem / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D017403:In Situ Hybridization; D020738:Leptin / Q000097:blood; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D020738:Leptin; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D012333:RNA, Messenger; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D006916:5-Hydroxytryptophan