Cimetidine

Histamine dihydrochloride was purchased from Sigma-Aldrich (St.louis, MO). The agonist of H1R, histamine trifluoromethyl toluidide dimaleate (HTM), the agonist of H2R, dimaprit dihydrochloride (DIM) and the antagonist of H2R, cimetidine (CIM) were purchased from Tocris Bioscience (Minneapolis, MN). The antagonist of H1R, pyrilamine maleate salt (PYR) was purchased from Sigma-Aldrich. HEC-1 endometrioid adenocarcinoma cell line and MCF-7 breast cancer cell line were obtained from the Health Science Research Resources Bank of Osaka, Japan. HMC-1 mastocytoma cell line was kindly provided from Dr. Kitamura (Osaka University, Osaka, Japan). The doses used in these experiments of these agonists and antagonists were adjusted to those in previous reports 8 (link),18 (link),19 (link).

Clobenpropit, trans-triprolidine, cimetidine, and histamine were purchased from Tocris Bioscience. For behavioral experiments, Clobenpropit was dissolved in saline and administered subcutaneously 45 minutes before the experiment at 5mg/kg unless otherwise stated. For hippocampal delivery, the drugs were dissolved in artificial cerebrospinal fluid (ACSF) and injected via bilateral guide cannulae using a microsyringe pump (1 μl/hemisphere) 15 minutes before the experiment at the following final concentrations: Clobenpropit, 10mM; trans-triprolidine, 0.5mM; and cimetidine, 1mM. Drug doses and concentrations were chosen based on previous studies (Pérez-García et al., 1999 (link); Xu et al., 2009 (link)). For slice electrophysiology, the drugs were dissolved in ACSF at the following final concentrations: Clobenpropit, 10 μM; trans-triprolidine, 2 μM; cimetidine, 50 μM; and histamine, 10 μM. Final concentrations were chosen based on pilot experiments and previous studies (Zhou et al., 2006 (link); Chepkova et al., 2012 (link)).