On the modulation of the cardiovascular reaction to startle stimuli in subjects at risk for developing primary hypertension
- Publisher: Freie Universität Berlin Universitätsbibliothek, Garystr. 39, 14195 Berlin
610 Medizin und Gesundheit | 610 Medical sciences; Medicine | blood pressure | startle reflex | amygdala | salt sensitivity | hypertension
INTRODUCTION: The startle reflex is a well established paradigm in psychophysiology. Reflex modulation by affective stimuli and the reaction of the heart rate are well known.
Salt sensitivity is considered a risk factor for the development of primary hypertension later in life. One possible explanation for this heightened risk is an enhanced affective reactivity that also modulates cardiovascular reactions (presumably mediated by an over-reactive amygdala). Enhanced cardiovascular reactions to mental stress and enhanced affective modulation of the startle reflex have both been demonstrated in salt sensitive subjects.
Therefore, the aim of this study was to investigate the cardiovascular reaction to startle stimuli and its modulation by affective stimuli in salt resistant and salt sensitive normotensives.
METHODS: 80 subjects were categorized as “salt resistant” and “salt sensitive”. To modulate the startle reflex, pictures from the categories “pleasant”, “unpleasant” and “neutral” from the “international affective pictures system” were used. Heart rate, blood pressure and skin conductance were recorded continuously.
RESULTS: A heart rate and blood pressure rise followed the startle stimulus. The reaction of the heart rate was modulated by the valence of the pictures, but the blood pressure reaction was enhanced in pleasant and unpleasant context. Salt sensitive subjects had an enhanced modulation of the eye blink and heart rate reaction, but a smaller and less modulated blood pressure reaction.
DISCUSSION: Salt sensitive subjects demonstrated an enhanced affective modulation of the heart rate reaction to startle stimuli. This finding supports the view of an over-reactive amygdala.
The modulation of the blood pressure reaction to startle stimuli appears to be an indicator for the arousal that is elicited by the pictures.
The smaller blood pressure reaction of salt sensitive subjects could be explained by stimulus characteristics or by a less flexibile blood pressure reaction.
An enhanced affective modulation of cardiovascular reactions, as well as a less flexible blood pressure regulation can contribute the development of primary hypertension later in life.