Preliminary Findings on Sex Differences in Response to Various Acute Stressors in Male and Female Mice

Purpose: Studies in both humans and animals have shown that pre-menopausal females are protected against the hypertensive and sympatho-excitatory effects of stress. Our goal was to identify whether sex difference exists between male and female mice in response to various acute stressors. Methods: Adult male (n=4) and female (n=4) C57BL/6J mice underwent telemetry implantation (HD-X10, DSI) surgery and allowed 1-week recovery. Each day the mice were exposed to 1 of 5 acute stressors (acute restraint, hypoxia, new cage, cold, or forced swim). Mice were allowed 1-2 days of recovery between stressors. Acute restraint: placing the mouse in a conical tube for 30 min; hypoxia: exposing the mouse to 20 min of 8% O2; new cage: placing the mouse in an empty cage with no bedding for 30 min; cold: exposing the mouse to 1-4C for 30 min; forced swim: placing the mouse in a water-filled beaker for 10 min. Mean arterial pressure (MAP), heart rate (HR), and activity were recorded and data analysis (2-way repeated measures ANOVA followed by Holm-Sidak) was performed. Results: Acute restraint: male mice responded with peak MAP of 135±4, peak HR of 768±21, and peak activity of 0.00±0.0; whereas female mice responded with peak MAP of 131±2, peak HR of 749±21, and peak activity of 0±0.0. Hypoxia: male mice responded with peak MAP of 122±4, peak HR of 780±6, and peak activity of 0.50±0.3; whereas female mice responded with peak MAP of 131±1, peak HR of 784±18, and peak activity of 0.50±0.3. New cage: male mice responded with peak MAP of 137±7, peak HR of 789±8, and peak activity of 1.75±0.5; whereas female mice responded with peak MAP of 137±4, peak HR of 790±3, and peak activity of 1.50±0.3. Cold: male mice responded with peak MAP of 133±4, peak HR of 800±9, and peak activity of 1.00±0.4; whereas female mice responded with peak MAP of 137±7, peak HR of 797±14, and peak activity of 1.50±0.3. Forced swim: male mice responded with peak MAP of 136±5, peak HR of 729±30, and peak activity of 1.50±0.3; whereas female mice responded with peak MAP of 134±5, peak HR of 694±7, and peak activity of 1.25±0.5. Conclusions: In this preliminary study, no significant sex difference was observed in male and female mice in response to the various acute stressors, however there was a trend for sex difference in MAP during acute restraint stress. This study needs to be repeated to increase sample size before further conclusions can be made.