Involvement of β-adrenergic receptor of nucleus tractus solitarius in changing of baroreflex sensitivity by estrogen in female rats.
BACKGROUND
Arterial baroreflex (ABR) is an important factor in preventing of blood pressure fluctuations that determined by baroreflex sensitivity (BRS). Estrogen is an ovarian hormone that has influence on ABR. The mechanism of this effect of estrogen unknown and may be mediated by β-adrenergic receptor of nucleus tractus solitarius (NTS), an important area in regulation of baroreflex. Therefore, in this study changing of BRS by estrogen after blockade β-adrenergic receptor of NTS in ovariectomized rats (Ovx) and Ovx treated with estrogen (Est) was examined.


METHODS
After ovariectomy, all female rats divided to Ovx and Ovx + Est groups and two series of experiments were performed. In the first experiment, phenylephrine was [intravenously, IV] injected in both the Ovx and Ovx + Est groups, and mean arterial pressure (MAP), heart rate (HR), and BRS were evaluated (n = 8 for each group). In the second experiment, each of Ovx and Ovx + Est groups divided into saline and propranolol (pro) groups, saline and pro stereotaxically were microinjected into NTS, respectively. Further, phenylephrine (IV) was injected in all groups and BRS was evaluated.


RESULTS
BRS significantly increased in estrogen-treated groups (Ovx + Est) compared to Ovx groups (P < 0.01). The blockade β-adrenergic receptor of NTS by pro did not significantly changed BRS in both Ovx and Ovx + Est groups.


CONCLUSIONS
We concluded that there aren't any intraction between estrogen and β-adrenergic receptor of NTS in BRS.
Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Ali Asghar
AA
Pourshanazari
Isfahan Payame Noor University, Isfahan, Iran.
Ozra
O
Mohagheghi
Isfahan Payame Noor University, Isfahan, Iran.
Ali A
AA
Pilavarian
Neurocognitive Research Center and Department of Physiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Lili
L
Enayatfard
Neurocognitive Research Center and Department of Physiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Mohammad N
MN
Shafei
Baroreflex sensitivity; Estrogen; Mean arterial pressure; Microinjection; Nucleus tractus solitarius; β-adrenergic receptor