DIFFERENCES IN STRESS REACTIVITY OF LABORATORY MACAQUES MEASURED BY HEART PERIOD AND RESPIRATORY SINUS ARRHYTHMIA

Some laboratory primates are more likely than others to react to anxie ty-provoking stressors. Individuals that overreact to stressors may ex perience diminished psychological well-being and would be inappropriat e for some experiments. The differences between reactive and nonreacti ve individuals may be reflected in heart period and respiratory sinus arrhythmia (RSA). Using surface electrodes and radio telemetry, we mea sured these two cardiac variables in seven male and ten female singly caged longtailed macaques (Macaca fascicalaris) when they were exposed to two stressors, a sudden noise (whistle test) and an unfamiliar tec hnician wearing capture gloves (glove test). Behavior was videotaped d uring both tests. For the whistle test, cardiac data were recorded bef ore, during, and after two 1 min whistle blasts separated by 90 min. F or the glove test, data were recorded in 1 min blocks every 8 min over 96 min before, during, and after 1 min exposure to the gloved technic ian. Heart period was decreased and RSA was suppressed during both the whistle and glove exposures. After the whistle test, the cardiac acti vity of most subjects returned to baseline levels within 10 min. The g love test produced more extended suppression, with greater individual differences, than the whistle test. There were greater individual diff erences in RSA than in heart period. These enhanced individual differe nces were used to define stress reactors that differed from nonreactor s in their cardiac data profiles. Of 16 subjects that completed the gl ove test, five were identified as reactors. (C) 1998 Wiley-Liss, Inc.