What makes stress stressful? Why the acute/chronic stress regime is incomplete.
February 12, 2014 @ 12:20 pm
to 01:10 pm
Gail McCormick, Penn State
104 Forest Resources Building
An organism s ability to respond to stress is integral to its survival and reproductive fitness and is increasingly important in light of environmental change. Stress is typically characterized by duration: acute stress is defined as lasting from a few minutes to a few days, while chronic stress is defined as lasting from days to months. In addition to characterizing stress by the duration of the application of the stressor itself (e.g. number of days of treatment/stressor), it is also characterized by outcome (e.g. chronic stress typically suppresses immune function whereas acute stress typically enhances immune function). This confusion in terminology, and resulting inconsistencies in the literature, hinders our ability to understand the consequences of stress. We propose that characteristics of stress other than duration are important. We systematically investigated how duration, frequency, and intensity of stress affect immune outcomes by experimentally manipulating levels of corticosterone (a "stress hormone") in Eastern fence lizards (Sceloporus undulatus) for 9 days and measuring the resulting immune response. We found that, although our low-dose acute stress treatment enhanced immune function (as expected), our high-dose acute treatments suppressed immune function; and, counter to expectations, our chronic stress treatment had no effect on the immune parameters we measured. Although three of our treatments received the same average amount of stress over the treatment period, we observed three different immune outcomes, highlighting the need to measure and report more than just the duration of stress if we are to understand the ecological consequences of stress.
Contact
David Watts
daw300@psu.edu