Clenbuterol

Cocaine hydrochloride (Qinghai Pharmaceutical Firm, China) was dissolved in 0.9% saline at 2 mg/ml for mouse CPP, 4 mg/ml for locomotor response test. Betaxolol (Tocris Bioscience, UK), a selective β1-AR antagonist, was dissolved in saline at 2 mg/ml and administered at a dose of 10 mg/kg (i. p.; Vranjkovic et al., 2012 (link); Al-Hasani et al., 2013 (link)). Clenbuterol (Tocris Bioscience, UK), a selective β2-AR agonist, was dissolved in saline at 1 mg/ml and administering at a dose of 5 mg/kg (i. p.; Heal et al., 1991 (link); Mellios et al., 2014 (link)). Control animals received an equivalent volume of saline.

Doses were calculated based on the salt forms. The drugs were dissolved in saline, neutralized to a pH of ∼7.4, and injected i.p. in a volume of 1 ml/kg body weight. The β₂-adrenergic receptor agonist clenbuterol and the β₂-adrenergic receptor antagonist ICI-118,559 were purchased from Tocris (Ballwin, MO) and Research Biochemical International (RBI; Natick, MA, United States), respectively. The 5-HT_2A/2B/2C receptor partial agonist DOI, (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride, was purchased from RBI. A dose of DOI (1.25 mg/kg, i.p.) producing a near-maximum of head shakes over a 30 min period was chosen for experiments testing suppression of head shakes by clenbuterol (Gewirtz and Marek, 2000 (link)). DOI-induced head shakes increase in a monotonic dose-dependent manner through 9 mg/kg using Sprague–Dawley rats (Pranzatelli, 1990 (link)). For the electrophysiological experiments, (-) epinephrine bitartrate was purchased from Sigma (St. Louis, MO, United States). A 1 M stock solution was prepared with 10 mM sodium metabisulfite and diluted appropriately for the final solution bath applied to the slice. 5-Hydroxytryptamine (5-HT) creatine sulfate was purchased from Sigma Chemical, Co. (St. Louis, MO, United States). 5-HT was used only to find cells in which 5-HT_2A receptor stimulation would induce late EPSCs.