Central L-arginine reduced stress responses are mediated by L-ornithine in neonatal chicks.
Recently, we observed that central administration of L-arginine attenuated stress responses in neonatal chicks, but the contribution of nitric oxide (NO) to this response was minimal. The sedative and hypnotic effects of L-arginine may be due to L-arginine itself and/or its metabolites, excluding NO. To clarify the mechanism, the effect of intracerebroventricular (i.c.v.) injection of L-arginine metabolites on behavior under social separation stress was investigated. The i.c.v. injection of agmatine, a guanidino metabolite of L-arginine, had no effect during a 10 min behavioral test. In contrast, the i.c.v. injection of L-ornithine clearly attenuated the stress response in a dose-dependent manner, and induced sleep-like behavior. The L-ornithine concentration in the telencephalon and diencephalon increased following the i.c.v. injection of L-arginine. In addition, several free amino acids including L-alanine, glycine, L-proline and L-glutamic acid concentrations increased in the telencephalon. In conclusion, it appears that L-ornithine, produced by arginase from L-arginine in the brain, plays an important role in the sedative and hypnotic effects of L-arginine observed during a stress response. In addition, several other amino acids having a sedative effect might partly participate in the sedative and hypnotic effects of L-arginine.
Suenaga
R
R
Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresources and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan.
Yamane
H
H
Tomonaga
S
S
Asechi
M
M
Adachi
N
N
Tsuneyoshi
Y
Y
Kurauchi
I
I
Sato
H
H
Denbow
D M
DM
Furuse
M
M
D000596:Amino Acids; D000818:Animals; D000831:Animals, Newborn; D001120:Arginine / Q000378:metabolism / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D001923:Brain Chemistry / Q000187:drug effects*; D002645:Chickens; D004027:Diencephalon / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006993:Hypnotics and Sedatives / Q000378:metabolism / Q000494:pharmacology*; D009952:Ornithine / Q000378:metabolism*; D013312:Stress, Physiological / Q000378:metabolism*; D013687:Telencephalon / Q000378:metabolism
D000596:Amino Acids; D006993:Hypnotics and Sedatives; D001120:Arginine; D009952:Ornithine