THE ACTION OF BROMOCRIPTIN AND SULPIRIDE ON MELANIN-CONCENTRATING HORMONE-PRODUCING NEURONS IN THE MEDIAL PREOPTICAL AREA IN LACTATING LONG-EVANS RATS (Rattus norvegicus)

• Grant number: 25/00659-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2025
• End date: April 30, 2027
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Jackson Cioni Bittencourt
• Grantee: Camila de Carvalho
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 23/02531-5 - The melanin-concentrating hormone peptidergic system: a multiprotocolary approach to a multifunctional analysis, AP.TEM

Abstract

This study aims to investigate the effects of Bromocriptine (Bro) and Sulpiride (Sul) administration on the expression of Melanin-Concentrating Hormone (MCH) neurons in the Medial Preoptic Area (MPOA) of lactating Long-Evans rats. MCH plays a crucial role in regulating motivated behaviors, including feeding and maternal care, particularly during lactation. Prolactin (PRL) is essential in this context, regulating milk production and directly influencing maternal behavior. Modulating PRL levels through the administration of Bromocriptine, a dopaminergic agonist, and Sulpiride, a dopamine D2 receptor antagonist, allows us to investigate how hormonal alterations affect MCH expression and associated neuroplasticity in the MPOA. The study will involve 105 Long-Evans rats, including 84 primiparous females and 21 males for breeding purposes. After mating, females will be individually housed in a controlled environment (22¿±¿2° C, 12-hour light-dark cycle) and randomly assigned to seven experimental groups: Bromocriptine Group (Bro), which will receive subcutaneous injections of Bromocriptine (500¿µg in saline with 10% ethanol) twice daily from postpartum day (PPD) 120 to PPD190; Bromocriptine Control Group (CB), which will receive injections of saline with 10% ethanol at the same times and days as the Bro group; Sulpiride until PPD190 Group (S19), which will receive intraperitoneal injections of Sulpiride (80¿mg/kg in 10¿mM tartaric acid solution diluted in 0.9% saline) once daily from PPD120 to PPD190; Sulpiride until PPD260 Group (S26), similar to the S19 group, but Sulpiride administration will continue until PPD26; Sulpiride Control until PPD190 Group (CS19), which will receive 10¿mM tartaric acid solution diluted in 0.9% saline on the same schedule as the S19 group; Sulpiride Control until PPD260 Group (CS26), similar to the CS19 group, with administration extended until PPD260; and Negative Control Group (CN), which will not receive any pharmacological treatment. On PPD190, blood samples will be collected for plasma PRL quantification via ELISA. Brains will be removed after transcardiac perfusion, and the MPOA will be dissected using the micro-punch technique for RNA extraction. RT-qPCR will evaluate MCH gene expression, and immunohistochemistry will be performed to identify and quantify MCH-positive neurons in the MPOA. Maternal behavior will be monitored and recorded through closed-circuit video recordings throughout the experimental period. It is anticipated that Bromocriptine administration will lead to reduced plasma PRL levels and a consequent decrease in MCH expression in the MPOA. At the same time, Sulpiride is expected to increase PRL levels and potentially elevate MCH expression. These findings will contribute to understanding the neuroendocrine mechanisms regulating maternal behavior and neuroplasticity during lactation, which might offer new insights into the interaction between PRL and MCH in the MPOA. (AU)