Conditioned and unconditioned stimulus send at fixed or randomized intervals: possible behavioral differences for the expression and extinction of conditioned fear memory

• Grant number: 20/02297-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2020
• End date: August 31, 2021
• Field of knowledge: Biological Sciences - Pharmacology - Neuropsychopharmacology
• Principal Investigator: Leonardo Resstel Barbosa Moraes
• Grantee: Gabriel Cheregato
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 17/24304-0 - New perspectives in the use of drugs that modify atypical neurotransmitters in the treatment of neuropsychiatric disorders, AP.TEM

Abstract

Fear Conditioning is a behavioral paradigm widely used for the study of aversive memory extinction. It involves making an association between a neutral or conditioned stimulus (CS; e.g. context, tone, light, smell, etc.) and their aversive consequences, or unconditioned stimulus (US; e. g. footshocks). Thus, the animals exhibit a conditioned response (CR), an innate behavioral reaction called freezing (total immobility of the animal, except breathing movements). If the CS is present in the absence of the US causes conditioned responses to extinguish. Objective: To investigate if there are changes in the retrieval of fear memory and its extinction when mice are submitted to a contextual fear conditioning (CFC) or to auditory cue conditioned fear extinction protocol (AFC), in which the US are issued at fixed or random intervals. Methods: BLC57 male mice will be submitted to an MCC extinction protocol: training 4x0.85mA /1s; extinction session of 20 min; and a 5-min extinction test session, in which the intervals between US will be fixed (30s) or randomized (30, 60 and 90s). Another group of male mice will be submitted to the AFC extinction protocol: training 4x0.85 mA /1s - each footshock preceded by 1s of a tone cue of 1kHz/70dB /1s - send at fixed (30s) or randomized (30, 60 and 90s) intervals; extinction session: 18 sounds emitted in fixed (30s) or random intervals (30, 60 and 90s), and in a different context from the training; and test, exposing the animals to 9 sounds at fixed (30s) or randomized (30, 60, 90s) intervals. In the final of CFC or AFC protocols, both groups also will be submitted to the elevated plus-maze and open field, the most used tests for measuring anxiety-like and locomotory/exploration activity behaviors in mice. (AU)