A robust diving response in the laboratory mouse.

ABSTRACT

The diving response is a coordinated physiological response to submersion under water and has been documented amongst all mammals tested to date. The physiological response consists of three primary reflexes an immediate bradycardia, apnea, and selective constriction of peripheral blood vessels. We hypothesized that mice would exhibit a diving response upon voluntary submersion into water typically seen in other mammals. In this study, telemeters that measure arterial pressure were implanted into male and female C57Bl/6J mice. These mice were trained to voluntarily dive underwater for a distance of 40 cm over a 4-6 s period. Just before the dive, the interbeat interval (IBI) was 87 ± 6 ms (mean ± SD) and diastolic pressure was 99 ± 14 mmHg. Underwater submersion caused (1) a dramatic bradycardia immediately at the onset of each dive, as IBI increased to 458 ± 104 ms, and (2) a large drop in diastolic pressure, to 56 ± 16 mmHg despite the elevation in peripheral resistance. Mice experienced a short bout (~ 2 s) of hypertension (diastolic pressure rose to 131 ± 17 mmHg) upon emergence. The bradycardia and hypotension appeared to be vagally mediated, since both these responses were blocked with atropine pre-treatment. These data demonstrate that the mouse exhibits a robust diving response upon voluntary submersion into water.