title: Circadian rhythms in blood pressure in free-ranging three-toed sloths (Bradypus variegatus).
abstract: Blood pressure (BP) profiles were monitored in nine free-ranging sloths (Bradypus variegatus) by coupling one common carotid artery to a BP telemetry transmitter. Animals moved freely in an isolated and temperature-controlled room (24 degrees C) with 12/12-h artificial light-dark cycles and behaviors were observed during resting, eating and moving. Systolic (SBP) and diastolic (DBP) blood pressures were sampled for 1 min every 15 min for 24 h. BP rhythm over 24 h was analyzed by the cosinor method and the mesor, amplitude, acrophase and percent rhythm were calculated. A total of 764 measurements were made in the light cycle and 721 in the dark cycle. Twenty-four-hour values (mean +/- SD) were obtained for SBP (121 +/- 22 mmHg), DBP (86 +/- 17 mmHg), mean BP (MBP, 98 +/- 18 mmHg) and heart rate (73 +/- 16 bpm). The SBP, DBP and MBP were significantly higher (unpaired Student t-test) during the light period (125 +/- 21, 88 +/- 15 and 100 +/- 17 mmHg, respectively) than during the dark period (120 +/- 21, 85 +/- 17 and 97 +/- 17 mmHg, respectively) and the acrophase occurred between 16:00 and 17:45 h. This circadian variation is similar to that observed in cats, dogs and marmosets. The BP decreased during "behavioral sleep" (MBP down from 110 +/- 19 to 90 +/- 19 mmHg at 21:00 to 8:00 h). Both feeding and moving induced an increase in MBP (96 +/- 17 to 119 +/- 17 mmHg at 17:00 h and 97 +/- 19 to 105 +/- 12 mmHg at 15:00 h, respectively). The results show that conscious sloths present biphasic circadian fluctuations in BP levels, which are higher during the light period and are mainly synchronized with feeding.
authors.affiliation: Departamento de Fisiologia e Farmacologia, Universidade Federal de Pernambuco, Recife, PE, Brasil. dfittipaldi@bol.com.br
authors.forename: D P F
authors.initials: DP
authors.lastname: Duarte
authors.forename: V L
authors.initials: VL
authors.lastname: Silva
authors.forename: A M
authors.initials: AM
authors.lastname: Jaguaribe
authors.forename: D P
authors.initials: DP
authors.lastname: Gilmore
authors.forename: C P
authors.initials: CP
authors.lastname: Da Costa
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D008297:Male; D012896:Sloths / Q000502:physiology*; D013686:Telemetry / Q000379:methods