title: Heart rate variability and baroreflex function in AT2 receptor-disrupted mice.
abstract: We adapted telemetry and sequence analysis employed in humans to mice and measured heart rate variability and the spontaneous baroreflex sensitivity in angiotensin II type 2 (AT2) receptor-deleted (AT2 -/-) and wild-type (AT2 +/+) mice with either deoxycorticosterone acetate (DOCA)-salt hypertension or N(omega)-nitro-L-arginine methylester hydrochloride (L-NAME) hypertension. Mean arterial pressure leveled during the day at 101+/-1 mm Hg and during the night at 109+/-1 mm Hg in AT2 receptor-deleted mice, compared with 98+/-2 mm Hg (day) and 104+/-2 mm Hg (night) in wild-type mice. Mean arterial pressure increased in AT2 receptor-deleted mice with L-NAME to 114+/-1 mm Hg (day) and 121+/-1 mm Hg (night), compared with 105+/-2 mm Hg (day) and 111+/-2 mm Hg (night), respectively. DOCA-salt also increased day and night blood pressures in AT2 receptor-deleted mice to a greater degree than in wild-type mice. Heart rate variability in the time and frequency domain was not different between AT2 receptor-deleted mice and AT2 receptor-deleted mice at baseline. Systolic blood pressure variability in the low frequency band was lower in AT2 receptor-deleted mice (0.6+/-0.1 ms2 versus 3.9+/-1.3 ms2) than in wild-type mice. Baroreceptor-heart rate reflex sensitivity was significantly increased in AT2 receptor-deleted mice compared with wild-type mice (3.4+/-0.6 versus 2.1+/-0.5 ms/mm Hg). These differences remained after DOCA-salt and L-NAME treatments. We conclude that activation of the AT2 receptor impairs arterial baroreceptor reflex function, probably by a central action. These data support the existence of an inhibitory central effect of the AT2 receptor on baroreflex function.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Helios-Klinikum-Berlin, Germany.
authors.forename: Volkmar
authors.initials: V
authors.lastname: Gross
authors.forename: Ralph
authors.initials: R
authors.lastname: Plehm
authors.forename: Jens
authors.initials: J
authors.lastname: Tank
authors.forename: Jens
authors.initials: J
authors.lastname: Jordan
authors.forename: Andre
authors.initials: A
authors.lastname: Diedrich
authors.forename: Michael
authors.initials: M
authors.lastname: Obst
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Luft
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000235:genetics / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D003900:Desoxycorticosterone / Q000494:pharmacology; D005838:Genotype; D006339:Heart Rate / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000235:genetics / Q000502:physiology*
chemical_list: D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D003900:Desoxycorticosterone; D019331:NG-Nitroarginine Methyl Ester