Effect of neuropeptideY on the T-type Ca^<2+> channel current

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T-type Ca^<2+> channel plays pivotal roles in regulating the excitability of the neurons and non-neuronal excitable cells. The neuropeptideY (NPY) is one of the most abundantly expressed neuropeptides in the central and peripheral nervous systems, and its distribution correlates well with that of T-type Ca^<2+> channel, suggesting a functional interaction with it. The aim of this study was to investigate the functional interaction. In the former half of this study, I used the undifferentiated NG108-15 cells, in which the expression of the T-type Ca^<2+> channel current was confirmed. I found that low doses of NPY significantly augmented the T-type Ca^<2+> channel current with whole cell patch-clamp technique using Ba^<2+> as the charge carrier. The NPY treatment shifted the I-V relationship negatively. Experiments using NPY receptor subtype-selective agonist/antagonists revealed that both Y_1 and Y_2 receptors additively involved in the augmentation of the current. Consistently, RT-PCR analysis showed the expressions of mRNAs for Y_1 and Y_2 receptors. In the later half, to investigate the functional interaction, which was shown in the NG 108-15 cells, in the brain preparation, I set up culture system of hippocampal slice, which was reported to express the proteins. I examined the voltage-dependent channel currents expressed in the CA1 pyramidal neurons with slice patch-clamp technique. Further work is needed to obtain the conclusion of the NPY's effect on the voltage-dependent channel currents.