Rat UCN1 and rat acylated ghrelin were purchased from Peptide Institute, Inc. (Osaka, Japan). Yohimbine hydrochloride, a selective α2‐AR antagonist, was purchased from Sigma‐Aldrich Chemical Co. (St. Louis, MO, USA). The GHS‐R1a antagonist, [D‐Lys3]‐GHRP‐6, was purchased from Bachem, Inc. (Torrance, CA, USA). These compounds were dissolved in saline when injected by IP and intravenous (IV) routes. Rikkunshito, a Japanese traditional Kampo medicine, was supplied from Tsumura & Co. in the form of a powdered extract obtained by spray‐drying a hot water extract mixture of the following eight crude drugs: Atractylodis lanceae rhizoma (4.0 g), Ginseng radix (4.0 g), Pinelliae tuber (4.0 g), Poria (4.0 g), Zizyphi fructus (2.0 g), Citri unshiu pericarpium (2.0 g), Glycyrrhizae radix (1.0 g), and Zingiberis rhizoma (0.5 g). Rikkunshito was dissolved in distilled water when injected by orogastric administration (PO). Other analytical reagents included commercially available highest‐purity products.
Treatments were performed on unanesthetized and lightly hand‐restrained rats using the following volumes: 10 μL/rat for ICV injection, 1 mL/kg for IP or IV injection through the tail vein, and 10 mL/kg for PO.
Treatments were performed on unanesthetized and lightly hand‐restrained rats using the following volumes: 10 μL/rat for ICV injection, 1 mL/kg for IP or IV injection through the tail vein, and 10 mL/kg for PO.