Effects of transcranial direct current stimulation on blood pressure and autonomic nervous system modulation in normotensive and hypertensive rats

Author(s)

Olivia Moraes Ruberti

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2024-03-05

Examining board members

Bruno Rodrigues; Maria Claudia Costa Irigoyen; Patricia Chakur Brum; Silvia Lacchini; Wilson Nadruz Junior

• Advisor: Bruno Rodrigues

Abstract

Problem Statement: The possibility of using brain stimulation techniques in arterial hypertension (AH), such as transcranial direct current stimulation (tDCS), may be promising for reducing blood pressure (BP), and the prefrontal cortex (PFC) seems to be the main target to achieve cardiovascular effects with this stimulation. Aims: This study aims to evaluate the impact of bimodal tDCS on hemodynamic, autonomic, metabolic variables, and neuronal activation of the PFC in Wistar (WH), Sprague Dawley (SD), and spontaneously hypertensive (SHR) rats. Methods: In this work, we divided our results into two studies. Animals were randomly assigned to three experimental groups: control rats, rats subjected to tDCS, and rats subjected to SHAM stimulation. Study 1: At the beginning of the protocol, animals underwent sham-tDCS or tDCS for 8 days, for 20 minutes each day. Food consumption was analysed during the 8 days. One day after this intervention period, animals underwent cannulation surgery for hemodynamic recordings. Study 2: The same tDCS protocols were used. BP was analyzed using telemetry probes implanted in the abdominal aorta during the 8-day intervention. After this period, animals underwent transcardiac perfusion, and PFC neuronal activity was analysed through FOS expression by immunohistochemistry. Results: Study 1: tDCS reduced food consumption, systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR) in the SHR-tDCS group compared to the SHR-SHAM group and did not alter diastolic blood pressure (DBP). For pulse interval variance (IP), RMSSD, and high frequency (HF), there was a main effect of strain and treatment, i.e., SHR animals showed a reduction in these variables compared to WH animals, and tDCS increased the values of these variables. Regarding low frequency (LF), there was a main effect of strain and treatment, i.e., SHR animals showed an increase in this variable compared to WH animals, and tDCS decreased the values of this variable. The 8-day tDCS intervention reduced the LF/HF ratio in the SHR-tDCS group compared to the SHR-SHAM group. Study 2: In SHR rats, SBP, DBP, and HR values increased during tDCS, remained elevated immediately after the intervention, and returned to baseline values 1 hour after stimulus cessation. tDCS reduced MAP and SBP variance 24 hours after the first stimulation. In both SD and SHR animals, there was a main treatment effect on neuronal activation of the pre-limbic cortex (PrL), i.e., FOS expression increased after tDCS compared to SHAM stimulation, regardless of the number of stimulations. In the infralimbic cortex (IL), tDCS increased neuronal activation in this region only in SHR animals. Conclusion: The results of this study showed that tDCS reduced BP and modulated the autonomic nervous system, as well as cortical neuronal activation in rats, with more pronounced effects in the hypertensive strain (AU)

• FAPESP's process: 19/02975-5 - Effects of transcranial direct-current stimulation (tDCS) on blood pressure of spontaneously hypertensive rats (SHR): a functional, inflammatory and epigenetic approach
• Grantee: Olivia Moraes Ruberti
• Support Opportunities: Scholarships in Brazil - Doctorate