An initial transient is followed by steady‐state regulation of blood pressure during hibernation bouts in the Syrian hamster

Hamster blood pressure and heart rate decrease during hibernation to conserve energy, but it is unclear how blood pressure changes over the course of a hibernation bout. We tested the hypothesis that blood pressure falls and then slightly recovers to a stable, regulated state during a hibernation bout. A blood pressure telemetry transmitter was implanted in a Syrian hamster (Mesocricetus auratus) for continuous recordings. Each hamster was placed in a 14:10 Light:Dark cycle at 23°C for 3 weeks and then transferred to a 8:16 Light:Dark cycle at 6°C. While euthermic, the hamster maintained mean arterial pressure at 87 ± 3 mmHg and heart rate at 352 ± 16 bpm at ambient temperatures of 23°C as well as at 6°C. Each hamster displayed multiple 3–5 day hibernation bouts. Each bout showed a two stage pattern: an initial, labile period (< 1 day) where mean pressure transiently decreased (for some bouts as low as 20 mmHg) and a steady period (2–4 days) where mean pressure was maintained at 46 ± 4 mmHg. Spontaneous baroreflex sensitivity, normalized to baseline heart rate, was −2.7 ± 1.5 and −6.7 ± 2.5 (during euthermia and hibernation, respectively). Data support the hypothesis that following a transient, mean arterial pressure is stable during a bout of hibernation. (Support: R01 HL091763)