Dl propranolol

DL-Propranolol, an antagonist of β-noradrenergic receptors that crosses the blood-brain-barrier, obtained from Sigma-Aldrich (France) was prepared in 0.9% saline (NaCl) and injected intraperitoneally at a dose of 10 mg/kg (Przybyslawski et al., 1999 (link); Conversi et al., 2014 (link)). NaCl and propranolol were both administered at a volume of 10 mL/kg. Mice received injections of propranolol or NaCl immediately after training for the consolidation procedure except for the CTA test in which the drugs were injected 25 min after the presentation of saccharin and therefore 5 min before LiCl injection. For the reconsolidation procedure, mice received injections of propranolol or NaCl just after reactivation, or the day following learning for the no-reactivation procedure. The memory test took place 24 h after injection. Consequently, animals were never tested under the influence of propranolol but the day after injection, when the drug was no longer present in the organism.

Bdph, a mixture of Z- and E-Bdph (85% and 15%, respectively), was prepared via a Perkin synthesis as previously described (Lin et al. 1984 ). 4-Aminopyridine (4-AP, ≥99%), aspaminol (≥98%), atenolol (≥98%), atropine (≥99%), caffeine (99%), diltiazem (≥99%), papaverine (≥98%), pentobarbital (≥98%), phenoxybenzamine (≥97%), prazosin (≥99%), dl-propranolol (≥99%), tetraethylammonium (TEA, ≥98%), tetrodotoxin (≥98%), verapamil (≥99%) and yohimbine (≥98%) were purchased from Sigma-Aldrich Chemical (St. Louis, MO). Other reagents, such as NaCl, KCl, CaCl₂, NaH₂PO₄, NaHCO₃ and dextrose, were analytical grade.
Male ICR mice weighing 23–25 g were purchased from the Animal Center of the Ministry of Science and Technology (Taipei, Taiwan). The animals were housed in ordinary cages at 22 ± 1 °C with a humidity of 50–60% under a constant 12 h light/dark cycle and provided with food and water ad libitum. Under a protocol approved (LAC 74-058) by the Animal Care and Use Committee of Taipei Medical University, the following in vitro experiments were performed.

All drugs were administered systemically at previously established doses and timepoints. Mifepristone (Generon, UK) was injected at 30 mg/kg (60 mg/ml in propylene glycol, s.c.) immediately after memory reactivation (Pitman et al. 2011 (link)). DL-propranolol (Sigma, UK) was injected at 10 mg/kg (10 mg/ml in saline, i.p.) immediately after reactivation (Debiec and LeDoux 2004 (link); Pitman et al. 2011 (link)). (+/−)-SKF38393 (Sigma, UK) was injected at 5 mg/kg (5 mg/ml in 5% DMSO in saline, i.p.) 5 min before reactivation (de Lima et al. 2011 (link)). Nefiracetam (Sigma, UK) was injected at 3 mg/kg (6 mg/ml in saline, i.p.) 1 h before reactivation (Yoshii et al. 1997 (link)). SCH23390 (Tocris, UK) was injected at 0.1 mg/kg (0.1 mg/ml in saline, i.p.) 30 min before reactivation (Heath et al. 2015 (link)). Modafinil (Sigma, UK) was injected at 5 mg/kg (10 mg/ml in 50% DMSO in saline, i.p.) 60 min prior to reactivation (Shanmugasundaram et al. 2015 (link)). All i.p. injections were administered to the same (right) side of the abdomen. Allocation to drug treatment was fully randomised within each experimental cohort of 8 rats.