Effects of multisession prefrontal cortex tDCS or taVNS on stress, perceived stress and sleep quality: a double-blind, randomized controlled study.

Introduction: Chronic stress is a condition characterized by prolonged stimulation, leading to mental and physical weakness. It can have detrimental effects on individuals' mental health and cognitive function, potentially causing various health issues. This article explores the potential of non-invasive neuromodulation techniques, specifically transcranial direct current stimulation (tDCS) and transcutaneous auricular vagus nerve stimulation (taVNS), in managing chronic stress and improving sleep quality. Methods: The study conducted a randomized, double-blinded, controlled trial with participants experiencing chronic stress. In total, 100 participants were randomly assigned to one of four conditions: the anodal tDCS group (n = 50), the sham tDCS group (n = 50), the taVNS group (n = 50), or the sham taVNS group (n = 50). Within each condition, participants received five sessions of either active treatment or sham treatment, with 20 min of tDCS over the dorsolateral prefrontal cortex (2 mA) for the tDCS groups, or taVNS on the left ear (20 Hz) for the taVNS groups. At baseline, post-intervention, and 4 weeks thereafter, we evaluated stress using the Lipp's Inventory of Stress Symptoms for Adults (LSSI), perceived stress through the Perceived Stress Scale (PSS-10), and sleep quality via the Pittsburgh Sleep Quality Index (PSQI). Results: The tDCS and taVNS interventions resulted in reduced stress levels, improved sleep quality, and enhanced perception of stress. Discussion: These findings suggest that tDCS and taVNS hold promise as effective treatments for chronic stress, offering a safe and accessible approach to improving individuals' wellbeing and overall quality of life. Clinical trial registration: https://ensaiosclinicos.gov.br/rg/RBR-2ww2ts8, identifier UTN: U1111-1296-1810; Brazilian Registry of Clinical Trials (REBEC) RBR-2ww2ts8.

Transcutaneous auricular vagus nerve stimulation modulates masseter muscle activity, pain perception, and anxiety levels in university students: a double-blind, randomized, controlled clinical trial.

Introduction: Chronic anxiety is a statemarked by sustained activation of the masseter muscle, manifesting in both mental and physical strain. This prolonged tension can significantly impact mental wellbeing and cognitive abilities, posing a risk for a range of health complications. This double-blind, randomized, controlled clinical trial investigated the impact of transcutaneous auricular vagus nerve stimulation (TAVNS) on masseter muscle activity, pressure pain threshold (PPT), and anxiety levels in university students with elevated anxiety. Methods: Forty-two participants meeting inclusion criteria were randomly assigned to either active TAVNS or sham TAVNS groups. Various parameters, including masseter muscle electromyographic (EMG) signals, PPT, and Beck Anxiety Inventory (BAI) scores, were assessed before pretreatment, immediately after the intervention week, and 2 weeks follow-up. Results: Active TAVNS significantly reduced both left and right masseter activation during resting mandibular position, persisting for 2 weeks post-intervention. Additionally, TAVNS induced a lasting decrease in both left and right masseter PPT, indicative of altered pain perception. Notably, BAI scores showed a substantial reduction, emphasizing TAVNS as a potential intervention for anxiety, with effects maintained at the 2-week follow-up. Discussion: This study provides comprehensive insights into the multifaceted effects of TAVNS on physiological and psychological aspects associated with anxiety in university students. The promising results underscore TAVNS as a potential neuromodulatory intervention for anxiety-related conditions, warranting further research and clinical exploration. Clinical Trial Registration: https://ensaiosclinicos.gov.br/rg/RBR-4s4kt2r.

Effects of repetitive pinprick stimulation on preterm offspring: Alterations in nociceptive responses and inflammatory hypersensitivity in adulthood.

INTRODUCTION: This study investigates the effects of repetitive pinprick stimulation on preterm offspring and its impact on nociceptive responses and inflammatory hypersensitivity in adulthood. OBJECTIVES: The objective is to shed light on the potential long-term consequences of neonatal pain and prematurity on sensory processing. METHODS: Term and preterm rats were subjected to repetitive pinprick (PP) stimulation or control (CC) during the neonatal period. Adult rats received CFA injection to induce inflammatory hypersensitivity, and mechanical hypersensitivity was measured. Gender differences in inflammatory hypersensitivity were also examined. Maternal behavior, litter weight, and offspring growth were monitored to assess any potential influences of the stimulation on these parameters. RESULTS: In preterm rats, the PP stimulation did not affect baseline thresholds to mechanical stimuli, but increased mechanical hypersensitivity after CFA injection in adult rats. Females exhibited greater inflammatory hypersensitivity compared to males. Maternal behavior, litter weight, and offspring growth were not influenced by the stimulation. PP stimulation during the neonatal period led to changes in nociceptive responses in adulthood, potentially altering sensory processing. CONCLUSION: PP stimulation in preterm rats during the neonatal period resulted in changes in nociceptive responses in adulthood, leading to increased inflammatory hypersensitivity. The study emphasizes how early development can significantly impact sensory processing and further highlights the potential long-term consequences of prematurity and neonatal pain on this processing.