Advanced Medical Sciences

Neurobiology

  • Professor: Haruyuki Kamiya
  • Phone: +81-11-706-5028
  • FAX: +81-11-706-7863
Neurobiology laboratory focuses on to study cellular and molecular mechanisms underlying synaptic transmission and plasticity in the brain. We are using electrophysiological as well as optical methods to monitor neuronal activity and intracellular Ca2+ dynamics. We mainly use tissue slices made from rodent brain, since this preparation offers excellent experimental system for quantitative application of drugs and also for fine manipulation of neurons under visual control. Currently, two faculty members and three graduate students are pursuing research to reveal unknown synaptic mechanism in the brain.

Research

Synapses are tunable elements in neuronal networks of the brain. Recent evidence suggested that the structure and function of synapses are not static, but change by experience during daily life. This modifiable nature is called as synaptic plasticity, and considered as a cellular correlate of memory traces. The studies of mechanism underlying long-term potentiation (LTP) in the hippocampus, which is a robust activity-dependent synaptic plasticity, are of significant interest not only for basic neurobiologists, but also for clinical neuroscientists engaged in development of new therapeutic strategies for dementia or related memory disorders. Especially, we are interested in the mechanism of presynaptic forms of plasticity in the hippocampus. For this purpose, we developed an optical method to monitor presynaptic Ca2+ and voltage transients. This technique allows examination of detailed cellular mechanisms for presynaptic forms of plasticity. Current projects include roles of presynaptic Ca2+ stores in LTP at hippocampal CA3 synapse as well as analysis of presynaptic expression mechanism underlying LTP at CA1 synapse.

Education

We are teaching several undergraduate and graduate courses. Neuroscience is a lecture course for undergraduate students of medical school and aiming at understanding basic neuroanatomy and neurobiology. We are also participating in premedical practice of anatomy and teaching gross anatomy of human brain. For graduate students, we offer advanced neurobiology lecture and laboratory course. At this moment in time, we use mainly Japanese for most lecture courses, but also try to use English terms as possible, to familiarize medical students with technical terms in English.

International Activities

In 2005, we collaborated with a visiting scholar from China (Harbin Medical University) to study the effects of a neuroactive substance with patch clamp technique in hippocampal slices. We also attended international meeting in the United States (Annual Meeting of Society for Neuroscience) in 2006 and 2007.
Fig1 1 Mossy fibers compose one of major excitatory projections within the hipppocampal network. Mossy fiber synapses express unique presynaptic long-term potentiation (LTP).
Fig2 2 Selective loading of presynaptic terminals and axons with fluorescent Ca2+ indicator by injection of the dye into the bundles of mossy fibers.
Fig3 3 Ca2+ store hypothesis for presynaptic LTP at the mossy fiber synapse. Ca2+ release from intracellular stores amplifies presynaptic Ca2+ transients in a use-dependent manner.

Selected Publications

1. Shimizu H, Fukaya M, Yamasaki M, Watanabe M, Manabe T, Kamiya H (2008) Use-dependent amplification of presynaptic Ca2+ signaling by axonal ryanodine receptors at the hippocampal mossy fiber synapse. Proc Natl Acad Sci USA 105: 11998-12003.
2. Uchigashima M, Fukaya M, Watanabe M, Kamiya H (2007) Evidence against GABA release from glutamatergic mossy fiber terminals in the developing hippocampus. J Neurosci 27: 8088-8100.
3. Azuma T, Enoki R, Iwamuro K, Kaneko A, Koizumi A. (2004) Multiple spatiotemporal patterns of dendritic Ca2+ signals in goldfish retinal amacrine cells. Brain Res 1023: 64-73.
4. Kamiya H, Ozawa S, Manabe T (2002) Kainate receptor-dependent short-term plasticity of presynaptic Ca2+ influx at the hippocampal mossy fiber synapses. J Neurosci 22: 9237-9243.
5. Kamiya H, Umeda K, Ozawa S, Manabe T (2002) Presynaptic Ca2+ entry is unchanged during hippocampal mossy fiber long-term potentiation. J Neurosci 22: 10524-10528.