Naloxonazine dihydrochloride

Stock solutions of a broad-spectrum opioid antagonist (naloxone hydrochloride (Tocris, Bristol, UK)), a μ-receptor antagonist (naloxonazine dihydrochloride (Tocris)), a δ-receptor antagonist (naltrindole hydrochloride (Tocris)) and a κ-receptor antagonist (nor-binaltorphimine dihydrochloride (Tocris)) were dissolved in pyrogen-free saline (PFS). Pilocarpine (1 mg/μl, Sigma-Aldrich, St. Louis, MO, USA) was also dissolved in PFS. The stock solutions were stored at 4 °C until use. Our previous results and others have indicated that the appropriate microinjection dosage for naloxonazine, naltrindole and nor-binaltorphimine to selectively block μ-, δ- and κ-opioid receptors, respectively, without interaction with other opioid receptor subtypes, is within 20 μg [12 , 13 , 32 (link), 33 (link)]. In the current study, naloxone, naloxonazine, naltrindole and nor-binaltorphimine were microinjected at a dose of 10 μg/μl, which according to our previous studies efficiently exhibits pharmacological blockade [12 , 13 ]. The total volume for each injection was 1 μl and the duration of injection was 3 to 5 min. Our previous study has demonstrated that microinjection of 1 μl solution into the CeA does not cause CeA lesion [34 (link)].