Effects of orexin A on BMP−receptor signaling in AtT20 cells. (A) After preculture, AtT20 cells were treated with the combination of orexin (ORX) and BMP−4 in serum−free media. After 24−h stimulation with orexin and 1−, 6−, and 24−h stimulations with BMP−4, total cellular RNA was extracted, and the mRNA expression levels of POMC were quantified by qPCR. The expression levels of target genes were standardized by the RPL19 level in each sample. (B) Cells were pretreated with ORX in serum−free media for 24 h. After 60-min stimulation with BMP−4, the cell lysates were subjected to immunoblot (IB) analysis using anti−pSmad1/5/9, anti−tSmad1, and anti−actin. (C) Cells were pretreated with ORX in serum−free media for 24 h. After 60−min stimulation with BMP−4, total cellular RNA was extracted, and mRNA levels of Id−1 were examined by qPCR. The expression levels of target genes were standardized by the RPL19 level in each sample. Results are shown as means ±SEM of data from at least three independent experiments. Statistical analysis was performed by ANOVA. Values with different superscript letters are significantly different at p < 0.05 (B,C). * p < 0.05 vs. between the control groups (A).