Multiple factors working in concert regulate blood pressure over a hibernation bout in the Syrian hamster

Abstract

Although blood pressure (BP) is regulated as hamsters enter hibernation, the detailed relationship between BP, heart rate (HR), and baroreflex sensitivity (BRS) is not known. We tested the hypothesis that multiple factors regulate BP over a hibernation bout. BP was recorded via a DSI telemetry transmitter in Syrian hamsters (Mesocricetus auratus). Hamsters were then placed into the cold (6±1°C, 8hr Light:16hr Dark) to induce hibernation. Five minute averages of systolic BP, HR and spontaneous BRS were analyzed with Nevrokard. The time for a decrease or increase from 90% to 10% (i.e. “fall or rise time”) of SBP, HR, and BRS were determined. On entry into hibernation (4 animals, 7 bouts total), fall time of HR (194±17 min) and BRS (211±21 min) were significantly (p<0.01) shorter than that of SBP (295±34 min). During the initial phase of entry into hibernation, BP and HR significantly decreased while BRS was maintained, indicating HR may be an important factor in regulating BP. During the later phase of entry, SBP continued to fall and BRS fell rapidly, indicating factors other than simply HR regulate BP. During arousal from hibernation, BRS recovery lagged behind BP and HR, and the rise time of HR, SBP and BRS were not significantly different. Results are consistent with the hypothesis and indicate that multiple factors, arranged in a specific temporal pattern, regulate BP over a hibernation bout. (support: R01 HL091763)