title: Temporal relationships of blood pressure, heart rate, baroreflex function, and body temperature change over a hibernation bout in Syrian hamsters.
abstract: 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.
authors.affiliation: Department of Neurobiology, Physiology, & Behavior, University of California, Davis, Davis, California;
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Horwitz
authors.forename: Sat M
authors.initials: SM
authors.lastname: Chau
authors.forename: Jock S
authors.initials: JS
authors.lastname: Hamilton
authors.forename: Christine
authors.initials: C
authors.lastname: Song
authors.forename: Julia
authors.initials: J
authors.lastname: Gorgone
authors.forename: Marissa
authors.initials: M
authors.lastname: Saenz
authors.forename: John M
authors.initials: JM
authors.lastname: Horowitz
authors.forename: Chao-Yin
authors.initials: CY
authors.lastname: Chen
mesh_terms: 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
keywords: arrhythmia; cold; hemodynamics; torpor
references.citation: BMC Physiol. 2011 Aug 17;11:13
references.pmid: 21849079
references.citation: J Comp Physiol B. 2011 Feb;181(2):299-309
references.pmid: 20981552
references.citation: Am J Physiol Regul Integr Comp Physiol. 2008 Oct;295(4):R1168-74
references.pmid: 18667715
references.citation: Ann N Y Acad Sci. 2001 Jun;940:324-37
references.pmid: 11458690
references.citation: Am J Physiol Regul Integr Comp Physiol. 2008 Feb;294(2):R639-50
references.pmid: 18032471
references.citation: Am J Physiol. 1988 Feb;254(2 Pt 2):H377-83
references.pmid: 3344828
references.citation: J Exp Zool. 1948 Oct;109(1):55-78
references.pmid: 18889755
references.citation: Am J Physiol. 1994 May;266(5 Pt 2):R1705-10
references.pmid: 8203654
references.citation: Am J Physiol Regul Integr Comp Physiol. 2001 Mar;280(3):R744-51
references.pmid: 11171653
references.citation: Am J Physiol Heart Circ Physiol. 2010 Feb;298(2):H594-600
references.pmid: 19966049
references.citation: Am J Physiol. 1950 Dec;163(3):566-74
references.pmid: 14799632
references.citation: Am J Physiol. 1988 Jan;254(1 Pt 2):R102-8
references.pmid: 3276222
references.citation: Am J Physiol. 1970 Dec;219(6):1772-8
references.pmid: 4320916
references.citation: J Hypertens Suppl. 1985 Dec;3(3):S79-81
references.pmid: 2856787
references.citation: Am J Physiol. 1977 May;232(5):R203-8
references.pmid: 871176
references.citation: J Hypertens. 1997 Apr;15(4):391-9
references.pmid: 9211174
references.citation: Annu Rev Med. 2011;62:79-93
references.pmid: 20854174
references.citation: Am J Physiol. 1968 Jan;214(1):115-21
references.pmid: 5634514
references.citation: Annu Rev Physiol. 1979;41:305-21
references.pmid: 373593
references.citation: J Cardiovasc Transl Res. 2010 Oct;3(5):559-69
references.pmid: 20559779
references.citation: Hypertension. 2004 Feb;43(2):306-11
references.pmid: 14707159
references.citation: Circulation. 1999 Apr 6;99(13):1760-6
references.pmid: 10190888
references.citation: Hypertension. 1995 May;25(5):1058-68
references.pmid: 7737717
references.citation: Age Ageing. 2002 Sep;31(5):359-64
references.pmid: 12242198
references.citation: Pediatr Emerg Care. 2012 May;28(5):475-80; quiz 481-2
references.pmid: 22561323
references.citation: Am J Physiol. 1959 Jan;196(1):15-22
references.pmid: 13617428
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 1999 Dec;124(4):383-91
references.pmid: 10682236
references.citation: Neuroscience. 2012 Aug 30;218:110-25
references.pmid: 22641087
references.citation: Cryobiology. 1984 Dec;21(6):593-614
references.pmid: 6394214
references.citation: Am J Physiol. 1958 Jul;194(1):83-91
references.pmid: 13559433
references.citation: Exp Physiol. 2006 Jan;91(1):59-72
references.pmid: 16239249
references.citation: Am J Physiol. 1976 Sep;231(3):810-6
references.pmid: 970460
references.citation: Cryobiology. 1987 Feb;24(1):74-81
references.pmid: 3816289
references.citation: Cell Tissue Res. 1990 Oct;262(1):99-104
references.pmid: 2257620
references.citation: J Physiol. 1963 Oct;168:477-99
references.pmid: 14067940
references.citation: Physiol Rev. 2003 Oct;83(4):1153-81
references.pmid: 14506303
references.citation: J Appl Physiol Respir Environ Exerc Physiol. 1977 Mar;42(3):420-5
references.pmid: 838661
references.citation: Am J Physiol Regul Integr Comp Physiol. 2011 Aug;301(2):R438-47
references.pmid: 21562095
references.citation: Acta Physiol Scand. 1954 Oct 20;32(1):28-38
references.pmid: 13206796
references.citation: Exp Physiol. 2006 Jan;91(1):37-49
references.pmid: 16210446
references.citation: J Physiol. 1998 Nov 1;512 ( Pt 3):927-38
references.pmid: 9769433
references.citation: J Physiol Sci. 2007 Feb;57(1):73-9
references.pmid: 17270061
references.citation: Am J Physiol. 1978 May;234(5):R178-82
references.pmid: 645935
references.citation: J Comp Neurol. 2011 Apr 1;519(5):933-56
references.pmid: 21280045
references.citation: Am J Physiol Heart Circ Physiol. 2006 Jul;291(1):H482-3
references.pmid: 16772526