Brain neuron culture, Ion channels and Signal transduction studies.
We are conducting molecular biological, physiological and cell biological investigations of the signal transduction mechanisms of neurotransmitter effects on brain neurons. For this purpose, we have developed a unique method of culturing neurons from specific brain nuclei such as cholinergic neurons from the basal forebrain and dopaminergic neurons from the substantia nigra and the ventral tegmental area; these nuclei are related to Alzheimer's and Parkinson's diseases as well as schizophrenia and drug abuse.
Our
research is focused on the actions of slow acting excitatory neurotransmitters
such as substance P, neurotensin, orexins (related to a sleep disorder, narcolepsy)
and ghrelin (related to obesity) on brain neurons. We are currently investigating
the effects of these transmitters on potassium channels and newly found transient
receptor potential (TRP) channels. Major emphasis is placed on the elucidation
of signal transduction mechanisms (G proteins and messengers such as PKC)
of these transmitter effects on ion channels. Currently, we are investigating
the interaction between these ion channels and G proteins by molecular biological
methods (the single-cell RT-PCR method, RNAi as well as mutation of channels
and G proteins) and electrophysiological techniques (whole-cell patch clamp,
single channel recording, and microinjection of DNA and antibodies with Eppendorf
microinjectors).
One of our research accomplishments is the establishment of a unique technique for primary culture of brain nuclei from postnatal rats. One of the advantages of using these primary cultures is that it is feasible to perform critical experiments on intracellular signal transduction.
Selected References
Hoang, Q.V., Bajic, D., Nakajima, S., and Nakajima, Y. (2003). Orexin (Hypocretin) effects on GIRK channels. J. Neurophysiol. 90: 693-702.
Bajic, D., Koike, M., Albsoul-Younes, A.M., Nakajima, S., and Nakajima, Y. (2002). Two different inward rectifier potassium channels are targets of transmitter induced modulation of nucleus basalis neurons. Proc. Natl. Acad. Sci. USA 99:14494-14499.
Albsoul-Younes, A.M., Sternweis, P.M., Zhao, P. Nakata, H., Nakajima, S., Nakajima, Y., and Kozasa, T. (2001). Interaction sites of the G protein ÿ-subunit with brain G protein-coupled inward rectifier K+ channel. J. Biol. Chem. 276:12712-12717.
Takano, K., Stanfield, P.R., Nakajima, S., and Nakajima, Y. (1995). Protein kinase C-mediated inhibition of an inward rectifier potassium channel by substance P in nucleus basalis neurons. Neuron 14:999-1008.
Velimirovic, B.M., Koyano, K., Nakajima, S., and Nakajima, Y. (1995). Opposing mechanisms of regulation of a G protein-coupled inward rectifier K channel in rat brain neurons. Proc. Natl. Acad. Sci. USA 92: 1590-1594.
Stanfield, P.R., Nakajima, Y., and Yamaguchi, K. (1985). Substance P raises neuronal membrane excitability by reducing inward rectification. Nature 315:498-501.