Meeting Abstract
Animals introduced to captivity are subjected to a multitude of stressors, including confinement, altered diet, and human presence and contact. Not surprisingly, captivity is a potent and reliable means of inducing chronic stress in wild animals. Physiological changes due to captivity include increased baseline heart rate, reduced or absent startle response, and altered baseline or stress-induced glucocorticoid levels. Some of these changes may be due to a high degree sympathetic nervous activation caused by high levels of epinephrine and norepinephrine, which also decrease heart rate variability. The use of alpha- or beta-blockers may be a tool to reduce the negative effects of chronic stress and help animals adjust more quickly to captivity. These drugs temporarily block the receptors for epinephrine or norepinephrine, and are frequently prescribed for anxiety in humans. We tested the effects of a short course of an alpha-blocker (phentolamine) and a beta-blocker (propranolol) during the first week of chronic stress in house sparrows (Passer domesticus). We hypothesized that after one week of captivity, compared to control birds, propranolol or phentolamine treatment would have (1) a lower baseline heart rate, (2) less sympathetic activity (i.e. higher heart rate variability), and (3) reduced change in glucocorticoid release. We found that propranolol blocked the increase in baseline glucocorticoids evident in saline-treated animals. Phentolamine, on the other hand, caused a decrease in nighttime heart rate variability, indicating increased nighttime sympathetic nervous activity. We conclude that at least propranolol appears to ameliorate the transition to captive conditions.
