Involvement of Dopaminergic D2 Receptors in the Expression of Defensive Behaviors Assessed in the Elevated Plus Maze and Elevated T-Maze

• Grant number: 24/02726-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2024
• End date: March 31, 2026
• Field of knowledge: Humanities - Psychology - Physiological Psychology
• Principal Investigator: Amanda Ribeiro de Oliveira
• Grantee: Aline Daiany Calerá
• Host Institution: Centro de Educação e Ciências Humanas (CECH). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 22/02986-0 - Involvement of dopaminergic mechanisms in conditioned and unconditioned fear: modulation by hormonal factors, AP.PNGP.PI

Abstract

Dopamine is a neurotransmitter that belongs to the catecholamine class, and among its range of functions, it is related to mechanisms underlying fear and anxiety. The role of different dopaminergic receptors in unconditioned fear is not yet well defined; however, some studies demonstrate that D2 receptors in the inferior colliculus (IC) play a role in modulating unconditioned aversive responses, indicating that a reduction in dopamine activity intensifies unconditioned fear. Sulpiride is a drug that antagonizes D2-like dopaminergic receptors and has helped in understanding the role of dopamine, especially D2-like dopaminergic receptors, in the mechanisms underlying conditioned and unconditioned fear. Studies conducted with female rats show a significant difference in fear and anxiety responses depending on the estrous cycle phase, highlighting the importance of further studies with females for a better understanding of the role of sex hormones in fear modulation. Thus, this study aims to analyze the involvement of D2-like dopaminergic receptors in the expression of defensive behaviors. For this purpose, 216 Wistar rats will be used, including 72 males and 144 females, weighing approximately 250 g. Sulpiride will be administered at doses of 20 and 40 mg/kg, and vehicle for controls. Subjects will be divided into groups of 12 animals each, and the elevated plus maze and elevated T-maze tests will be performed. Our hypothesis is that, due to the D2 antagonistic action of sulpiride, fear expression will be potentiated in rats, and a difference in this expression may possibly be observed among females depending on the estrous cycle phase.