The objectives of this research.DrugsMidazolam (MDZ, Gobbi Novag SA) was diluted in sterile isotonic saline (SAL, 0.9 w/v) to a concentration of three mg/mL, and administered intraperitoneally (i.p.). The total volume of drug or equivalent volume of SAL was 1.0 mL/kg in all situations. This dose of MDZ was selected on the basis of previous reports demonstrating its capability to block contextual fear memory reconsolidation in Wistar rats (Bustos et al. 2009).ApparatusContextual fear conditioning was performed inside a 24 cm long 22 cm wide 22 cm high Plexiglas chamber with opaque gray walls in addition to a removable transparent ceiling, the floor consisting of 20 parallel stainless-steel grid bars, every single measuring 3 mm in diameter, spaced 1 cm apart, and connected to a device to supply adjustable foot shocks (Automatic Reflex Conditioner 7501, Ugo Basile). The chamber was cleaned with water and dried with paper towels ahead of and following all subjects. Recording of behavior (for offline evaluation) was made using a DCR-SR21 Sony Handycam digital video camera placed 50 cm above the conditioning chamber. Background noise was supplied with ventilation fans. All procedures were produced in a sound-isolated experimental room. Experiments were constantly performed throughout the light phase on the cycle.Behavioral proceduresIn all experiments, rats had been very first identified, weighed, and handled for five min on two separate days to habituate them to experimental manipulation. In these experiments involving i.p. injections, rats have been also injected with 1 mL/kg SAL after handling was total to habituate them to this process.Contextual worry conditioningOne day immediately after habituation procedures ended, rats were taken out individually from their home cage, transported in to the experimental area, and exposed towards the conditioning chamber for 3 min (preshock period), just after which two foot shocks (1.0 mA, 3-sec duration, with an inter-shock interval of 30 sec) serving as USs were delivered. Promptly right after the second shock ended, rats were removed from the chamber, transported back to the colony space, and placed back in their home cages.Reactivation sessionReactivations were often carried out 72 h immediately after conditioning. Rats were reexposed to the conditioning chamber, with no foot shock, for various periods of time (1, 4, or 5 min), according to the experiment.Drug administrationIn Experiment 1, MDZ 3 mg/kg or an equivalent volume of SAL was injected i.p. promptly right after reactivation sessions.Materials and MethodsSubjectsMedChemExpress 1400W (Dihydrochloride) subjects had been experimentally naive, adult male Wistar rats (60 to 65-d old, weighing 27020 g at the beginning on the experiments). Animals PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/20110535 have been bred in our colony within the Laboratorio de Psicologia Experimental, Facultad de Psicologia, Universidad Nacional de Cordoba, Argentina. All animals had been housed in stanwww.learnmem.orgExtinctionExtinction consisted of exposing rats to the conditioning chamber during 11, 14, or 15 min, according to the experiment. Having said that, in all groups receiving reactivation and extinction, the total level of context exposure was always 15 min (no matter whether it was 15 min straight or divided in 1/14 or 4/11).Learning MemoryMemory destabilizationReacquisitionIn Experiment 5 reacquisition consisted of a 3-min preshock period followed by only a single 3-sec shock of 0.5 mA (half the number [2] and intensity [1.0] of US compared to initial conditioning), soon after which rats had been straight away removed in the chamber and taken back to their dwelling cages inside the colony area.ExperimentRa.
