Temporal relationships of blood pressure, heart rate, baroreflex function, and body temperature change over a hibernation bout in Syrian hamsters.
Hibernating mammals undergo torpor during which blood pressure (BP), heart rate (HR), metabolic rate, and core temperature (TC) dramatically decrease, conserving energy. While the cardiovascular system remains functional, temporal changes in BP, HR, and baroreceptor-HR reflex sensitivity (BRS) over complete hibernation bouts and their relation to TC are unknown. We implanted BP/temperature telemetry transmitters into Syrian hamsters to test three hypotheses: H-1) BP, HR, and BRS decrease concurrently during entry into hibernation and increase concurrently during arousal; H-2) these changes occur before changes in TC; and H-3) the pattern of changes is consistent over successive bouts. We found: 1) upon hibernation entry, BP and HR declined before TC and BRS, suggesting baroreflex control of HR continues to regulate BP as the BP set point decreases; 2) during the later phase of entry, BRS decreased rapidly whereas BP and TC fell gradually, suggesting the importance of TC in further BP declines; 3) during torpor, BP slowly increased (but remained relatively low) without changes in HR or BRS or increased TC, suggesting minimal baroreflex or temperature influence; 4) during arousal, increased TC and BRS significantly lagged increases in BP and HR, consistent with establishment of tissue perfusion before increased TC/metabolism; and 5) the temporal pattern of these changes was similar over successive bouts in all hamsters. These results negate H-1, support H-2 with respect to BP and HR, support H-3, and indicate that the baroreflex contributes to cardiovascular regulation over a hibernation bout, albeit operating in a fundamentally different manner during entry vs. arousal.
['Horwitz|Barbara A|BA|', 'Chau|Sat M|SM|', 'Hamilton|Jock S|JS|', 'Song|Christine|C|', 'Gorgone|Julia|J|', 'Saenz|Marissa|M|', 'Horowitz|John M|JM|', 'Chen|Chao-Yin|CY|']
D000818:Animals D001143:Arousal D017704:Baroreflex D001794:Blood Pressure D018660:Blood Pressure Monitoring, Ambulatory D001833:Body Temperature Regulation D006224:Cricetinae D015716:Electrocardiography, Ambulatory D004734:Energy Metabolism D005260:Female D006339:Heart Rate D006605:Hibernation D008297:Male D008647:Mesocricetus D013686:Telemetry D013997:Time Factors
torpor arrhythmia cold hemodynamics