TY - JOUR
T1 - Sympathetic component of baroreflex control of heart rate is impaired in hypertension-prone (SBH) sabra rats
AU - Schorer-Apelbaum, Donna
AU - Weinstock, Marta
AU - Ben-Lshay, Drori
PY - 1984/6
Y1 - 1984/6
N2 - Baroreflex control of heart rate in response to phenylephrine was studied in conscious Sabra hypertension-prone (SBH) rats, at a prehypertensive stage, and hypertension-resistant (SBN) rats. Baroreflex sensitivity as determined from the slope of the relationship of mean arterial blood pressure and heart period was significantly lower in SBH rats (0.58 ± 0.06 versus 1.71 ± 0.11 ms/mmHg in SBN rats, P < 0.01) before the development of hypertension. Sympathetic nerve blockade with guanethidine (15 mg/kg) significantly reduced the slope of the mean arterial blood pressure-heart period relationship in SBN rats to 0.45 ± 0.05 ms/mmHg (P < 0.01) and increased the pressor response to phenylephrine, without having any effect on these parameters in SBH rats. Atropine methyl nitrate (1 mg/kg) abolished reflex vagal bradycardia in response to phenylephrine in both groups of rats. This suggests that SBH rats are unable to withdraw the sympathetic cardiac component of the baroreflex in response to a pressor stimulus and appear to rely only on increased vagal activity to effect bradycardia.
AB - Baroreflex control of heart rate in response to phenylephrine was studied in conscious Sabra hypertension-prone (SBH) rats, at a prehypertensive stage, and hypertension-resistant (SBN) rats. Baroreflex sensitivity as determined from the slope of the relationship of mean arterial blood pressure and heart period was significantly lower in SBH rats (0.58 ± 0.06 versus 1.71 ± 0.11 ms/mmHg in SBN rats, P < 0.01) before the development of hypertension. Sympathetic nerve blockade with guanethidine (15 mg/kg) significantly reduced the slope of the mean arterial blood pressure-heart period relationship in SBN rats to 0.45 ± 0.05 ms/mmHg (P < 0.01) and increased the pressor response to phenylephrine, without having any effect on these parameters in SBH rats. Atropine methyl nitrate (1 mg/kg) abolished reflex vagal bradycardia in response to phenylephrine in both groups of rats. This suggests that SBH rats are unable to withdraw the sympathetic cardiac component of the baroreflex in response to a pressor stimulus and appear to rely only on increased vagal activity to effect bradycardia.
KW - Baroreflex sensitivity
KW - Phenylephrine
KW - Sabra hypertension-prone rats (SBH)
KW - Sabra hypertension-resistant rats (SBN)
KW - Sympathetic control
KW - Vagai control
UR - http://www.scopus.com/inward/record.url?scp=0021237334&partnerID=8YFLogxK
U2 - 10.1097/00004872-198406000-00006
DO - 10.1097/00004872-198406000-00006
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C2 - 6530541
AN - SCOPUS:0021237334
SN - 0263-6352
VL - 2
SP - 257
EP - 260
JO - Journal of Hypertension
JF - Journal of Hypertension
IS - 3
ER -