Effect of Neuropeptide Y on the T-type Ca^<2+> Channel Current Expressed in NG108-15 Cells

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The distribution of neuropeptide Y (NPY) correlates well with that of the T-type Ca^<2+> channel in the central and peripheral nervous systems, suggesting a functional interaction between them. Here, we report that NPY significantly augmented the T-type Ca^<2+> channel current expressed in undifferentiated NG108-15 cells using Ba^<2+> as the charge carrier. Although the extent of augmentation was small (9.8%), the NPY treatment shifted the I-V relationship negatively. L-152, 804, a NPY-Y_5 receptor-selective antagonist, had no effect on the augmentation, whereas BIBP3226, a Y_1 receptor-selective antagonist, significantly suppressed the augmentation to 39.4%. Likewise, NPY (13-36), a Y_2-selective agonist, had a partial (43.7%) but significant augmentative effect on the T-type Ba^<2+> current. Consistently, RT-PCR analysis confirmed the expressions of mRNAs for Y_1 and Y_2 receptors but not that for Y_5 receptor, suggesting an additive contribution of the subtypes. Thus, NPY may play a role in regulating excitability via the augmentation of the T-type Ca^<2+> channel current.