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| Research |
1. Neural basis of learning, memory and social behavior
Chick or quail chick have advanced level of visual and auditory performance at the time of
hatching and show interesting behaviors such as imprinting (learn the characteristics of
the hen and follow it). Imprinting is a good model of learning, memory and social
behavior during infancy. We aim at
elucidating the development of plasticity of neural circuit and neurons
which supports the acquirement and retention of memory, or development
of social behavior by using behavioral, physiological, histological and
molecular biological methods. Since the avian embryonic brain can be manipulated
by ablation, transplantation, or introduction of various genes, birds are
useful model for investigating development of behavior and nervous system.
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2. Neural basis of sexual dimorphic differentiation of brain and behavior
Experimental evidence indicates that the sexual hormone secreted from gonads
during the perinatal period acts on the developing brain to induce masculine
or feminine pattern of neural differentiation. This organizational effect
leads to sex difference in brain and behavior. However, there exists phenomenon
which cannot be explained only by this mechanism. This suggests that the
sex of the brain itself may also have a direct role in the sexual differentiation.
To clarify this point, we construct brain chimera between male and female
embryo and analyze its behavior, reproductive function, brain histology
and gene expressions. We also study the function of genes which are differentially
expressed in male and female brain by activating or inactivating the genes.
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3. Neural basis of metabolic regulation
The brain is indispensable for the homeostasis of higher organisms. In
particular, energy balance is strictly controlled. Defects in this control
result in leanness or obesity, and cause several diseases including diabetes.
We focus on how this balance is acquired and maintained by the cooperative
activity of brain, digestive system and adipose tissue.
Bombesin-like peptides, gastrin-releasing peptide (GRP) and neuromedin
B (NMB) are neurotransmitters in both brain and gastrointestinal tracts.
These peptides bind to the G-protein coupling receptors on the cell surface
and activate intracellular cascades to exert their functions. GRP receptor
(GRPR), NMB receptor (NMBR) and the third structurally related receptor,
bombesin-like peptide receptor subtype 3 (BRS3), which is an orphan receptor,
were cloned to date. Bombesin-like peptides are involved in various physiological
functions such as food intake, digestion, metabolism, body temperature,
fear memory, stress response, circadian rhythm, itch response, reproductive
behavior, brain development and proliferation of cancer cells. Therefore,
elucidating neural mechanism by which these functions appear is important
for understanding the related disease or developing its new treatment.
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