Clorgyline inhibits orexin-A-induced arousal in layer-type chicks.

We previously demonstrated that intracerebroventricular (ICV) injection of orexin-A induces arousal and increased metabolic turnover rates of norepinephrine, dopamine, and serotonin in layer (egg-type) chicks. Because monoamine oxidase-A (MAO-A) is a potent degrading enzyme of these monoamines, we hypothesized that orexin-A may mediate its arousal-inducing effects through MAO-A. Therefore, we simultaneously injected clorgyline, a specific inhibitor of MAO-A, with orexin-A and examined behavior of chicks.

Chronic L-tyrosine alters the locomotor activity and brain monoamine levels in Roborovskii hamsters.

The Roborovskii hamster (Phodopus roborovskii) has high locomotor activity (hyperactivity) and low dopamine levels in the brain compared with the congeneric Djungarian hamster (Phodopus sungorus). To clarify the efficacy of dietary l-tyrosine in ameliorating signs of hyperactivity, we investigated the effects of chronic administration of l-tyrosine, the primary precursor of dopamine, on locomotor activity and brain monoamine levels in Roborovskii hamsters. Chronic supplementation of l-tyrosine had no effect on locomotor activity in the open field, but did decrease locomotor activity in the home cage.

Intracerebroventricular injection of orexin-A stimulates monoamine metabolism but not HPA axis in neonatal chicks.

We investigated the effects of intracerebroventricular (ICV) injection of orexin-A on plasma corticosterone (CORT) concentration and brain monoamine metabolism to clarify the mechanism by which ICV orexin-A induced arousal in chicks. In Experiment 1, plasma CORT concentrations were measured as an indicator of hypothalamic-pituitary-adrenal (HPA) axis activity. There was no significant difference in CORT concentration between the control and orexin-A administered groups.

Central L-ornithine, but not polyamines, induces a hypnotic effect in neonatal chicks under acute stress.

To clarify whether L-ornithine and/or its metabolite involves sedative and hypnotic effects under social separation stress, the effects of intracerebroventricular (i.c.v.

Oral administration of L-serine reduces the locomotor activity of socially isolated rats.

L-Serine is considered a functional amino acid in the central nervous system, since intracerebroventricular injection of L-serine induced sedative and hypnotic effects in neonatal chicks exposed to acute stressful conditions. Accordingly, L-serine is a candidate anti-stress factor, but the effect of daily intake of L-serine on behavior of animals exposed to chronic stress has not been investigated. In the present study, we exposed rats to social isolation stress for 4 weeks, and home cage test and open field test were concluded to evaluate the effect of L-serine on behavior.

Central l-proline attenuates stress-induced dopamine and serotonin metabolism in the chick forebrain.

Using microdialysis, we investigated the effect of l-proline on monoamine release in the medio-rostral neostriatum/hyperstriatum ventrale (MNH) of freely moving and restricted chicks. A 30 min handling-stress resulted in a significant increase in extracellular homovallinic acid (HVA), a dopamine metabolite, and 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite, in the MNH. l-Proline, perfused through the microdialysis probe into the MNH during the stressed condition, significantly attenuated the average dialysate concentration of HVA produced by handling-stress.

L-DOPA attenuates hyperactivity of Roborovskii hamsters.

The Roborovskii hamster (Phodopus roborovskii) has been shown to have high locomotor activity (hyperactivity) and low dopamine concentrations in the brain. We hypothesized that low brain dopamine concentrations play a role in the pathogenesis of hyperactivity. In this study, therefore, we investigated the effects of L-DOPA (L-3,4-dihydroxyphenylalanine), the precursor of dopamine, on the locomotor activity of Roborovskii hamster to verify the above hypothesis.

l-Serine induces sedative and hypnotic effects acting at GABA(A) receptors in neonatal chicks.

Intracerebroventricular injection of l-serine has been shown to have sedative and hypnotic effects on neonatal chicks exposed to acute stressful conditions. However, the mechanism by which l-serine induces these effects is unclear. The present study was conducted to clarify the mechanism by l-serine.