Publications by authors named "Kousuke Hamasu"

Throughout life, we are exposed to a variety of stresses, which may be inevitable and noxious sometimes. During evolution, animals must have acquired some physiological means to counteract stress. Vascular endothelial growth factor (VEGF) is an angiogenic and neurogenic factor, which has been shown to elicit antidepressant-like effects in response to different external stimuli, potentially functioning as an anti-stress molecule.

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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.

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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.

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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.

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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.

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Elastic fibers in the dermis play an important role in skin elasticity. The desmosine crosslinking structure constructed of lysyl oxidase (LOX) in elastic fibers contributes to elasticity, while elastic fibers are primarily degraded by one of the matrix metalloproteinases (MMPs), MMP-12. We investigated the gender differences and diurnal variation of these enzymes.

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Two species of the genus Phodopus, Djungarian hamster (P. sungorus) and Roborovskii hamster (P. roborovskii), differ in their behavior.

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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.

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