Stress-responsiveness influences baseline glucocorticoid levels: Revisiting the under 3 min sampling rule

Abstract

Plasma glucocorticoid (CORT) levels collected within 3min of capture are commonly believed to reflect pre-stressor, baseline CORT levels. Differences in these "baseline" values are often interpreted as reflecting differences in health, or the amount of social and environmental stress recently experienced by an individual. When interpreting "baseline" values it is generally assumed that any effect of capture-and-handling during the initial sampling period is small enough and consistent enough among individuals to not obscure pre-capture differences in CORT levels. However, plasma CORT increases in less than 3min post-capture in many free-living, endothermic species in which timing has been assessed. In addition, the rate of CORT secretion and the maximum level attained (i.e., the degree of stress-responsiveness) during a severe stressor often differs among individuals of the same species. In Florida scrub-jays (Aphelocoma coerulescens), an individual's stress-responsiveness during a 30min post-capture stressor is correlated with CORT levels in samples collected within 1.5min of capture, suggesting there is an intrinsic connection between stress-responsiveness and pre-capture CORT levels. Although differences in stress-responsiveness accounted for just 11% of the variance in these samples, on average, higher stress-responsive jays (top third of individuals) had baseline values twice that of lower stress-responsive jays (bottom third). Further, plasma CORT levels begin to increase around 2min post-capture in this species, but the rate of increase between 2 and 3min differs markedly with CORT increasing more rapidly in jays with higher stress-responsiveness. Together, these data indicate that baseline CORT values can be influenced by an individual's stress response phenotype and the differences due to stress-responsiveness can be exaggerated during sample collection. In some cases, the effects of differences in stress-responsiveness and the increase in CORT during sample collection could obscure, or supersede, differences in pre-capture plasma CORT levels that are caused by extrinsic factors.

Are 3 minutes good enough for obtaining baseline physiological samples from teleost fish?

“…These authors concluded that sampling should occur within 2 min of capture, with 3 min being the uppermost limit (Romero and Reed 2005). Small et al (2017) came to similar conclusions (ϳ2 min). Within the teleost literature, most blood samples appear to be collected within 3 min of the animal's capture (e.g., Knapp and Neff 2007;Cook et al 2012).…”

Does variation in glucocorticoid regulation predict fitness? A phylogenetic meta-analysis

“…We also recorded the length of the standardized period of restraint used prior to collecting a blood sample for stress-induced GCs. The time between stressor exposure and peak stress-induced GCs varies across species and individuals, and most species peak after 14-60 minutes of restraint (Breuner et al ., 2008; Satterthwaite et al ., 2010; Small et al ., 2017). We chose to accept authors’ selected timeframes as an acceptable measure for stress-induced GCs.…”

Impact of Fkbp5 × Early Life Adversity × Sex in Humanized Mice on Multidimensional Stress Responses and Circadian Rhythmicity

“…To enable spatial discrimination, navigation objects with differing shape and color were placed outside of the left and right arm of the arena. The whole process from cage opening to collection of the last drop was carried out within less than 1.5 minutes to avoid a procedure-associated rise of corticosterone [37]. Plasma aliquots were frozen immediately.…”