Threat Perception and Sympathetic Baroreflex Function during Mental Stress in Humans

Muscle sympathetic nerve (MSNA) reactivity to mental stress is highly variable between individuals. Recent research has reported a positive relationship between MSNA responsiveness and perception of a mental stress task as a threat (i.e., stress exceeds coping ability) versus a challenge (i.e., coping ability exceeds stress). Whether threat perception impacts sympathetic baroreflex function during mental stress remains unknown. In the present study, we hypothesized that spontaneous sympathetic baroreflex sensitivity (sBRS) would be reduced to a greater extent during stress in individuals who endorse a threat versus a challenge perception. Continuous heart rate (electrocardiography), beat-to-beat blood pressure (finger plethysmography), and MSNA (microneurography) were assessed during a 10-minute baseline and the speech preparation phase of the Trier Social Stress Test (TSST) in 14 healthy adults (9 males, 5 females, age: 21±4 years, body mass index: 24±3 kg/m 2 ). Participants rated their perceived stress and coping following the speech preparation using a visual scale ranging from 1 (not at all stressful/unable to cope) to 7 (extremely stressful/able to cope). The ratio of these values (i.e., stress-to-coping) was then used to determine whether each participant perceived the task as a threat (>1) or a challenge (≤1). The diastolic blood pressure (DBP) at which there is a 50% likelihood of an MSNA burst occurring (i.e., T50), and spontaneous sBRS were calculated during the baseline and speech preparation phases. Other phases of the TSST (i.e., speech and mental arithmetic) were not included due to changes in other parameters such as respiratory patterns, which may influence baroreflex assessment. Speech anticipation led to an increase in DBP (base: 63±5 vs. prep: 68±5 mmHg, p<0.001) and heart rate (base: 65±6 vs. prep: 72±8 beats/min, p<0.001), reduced MSNA (base: 20±9 vs. prep: 16±7 bursts/min, p<0.001), and unchanged spontaneous sBRS (base: -3±1 vs. prep: -3±2 bursts/100hb/mmHg, p=0.451) and T50 (base: 57±6 vs. prep: 57±8 mmHg, p=0.733). No correlation was found between threat perception and changes in spontaneous sBRS (r=-0.213, p=0.465), MSNA (r=-0.093, p=0.753), or heart rate (r=-0.288, p=0.319). However, threat perception was positively associated with changes in T50 (r=0.617, p=0.019) and DBP (r=0.613, p=0.020), whereby individuals who endorsed a threat perception demonstrated augmented increases in the T50 value and DBP reactivity to anticipatory stress. These results indicate that spontaneous sBRS is not influenced by differing perceptions of mental stress (i.e., threat vs. challenge). However, T50 increases to a greater extent in those who perceive the speech preparation as a threat, and this increase is associated with elevated DBP. The increased T50 associated with an elevated DBP may explain the positive relationship between MSNA responsiveness and threat perception to mental stress in humans. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.