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(Hypertension. 2004;43:270.)
© 2004 American Heart Association, Inc.

Scientific Contributions

Alterations in Sympathetic Ganglionic Transmission in Response to Angiotensin II in (mRen2)27 Transgenic Rats

Azeez A. Aileru; Exazevia Logan; Michael Callahan; Carlos M. Ferrario; Detlev Ganten; Debra I. Diz

From the Winston-Salem State University (A.A.A.), Winston-Salem, NC; Wake Forest University School of Medicine (E.L., M.C., C.M.F., D.I.D.), Winston-Salem, NC; and the Max Delbruck Center for Molecular Medicine (D.G.), Berlin, Germany.

Correspondence to Dr Azeez Aileru, Biomedical Research Infrastructure Center, Winston-Salem State University, 115 S Chestnut St, Winston-Salem, NC 27101. E-mail ailerua{at}wssu.edu

Hypertension in (mRen2)27 transgenic rats is partly dependent on activation of the sympathetic nervous system, but the role of ganglionic transmission is unknown. We assessed indices of synaptic plasticity (post-tetanic short-term potentiation [PTP] and long-term potentiation [LTP]) and sympathetic ganglionic transmission without tetany in superior cervical ganglia (SCG) of Hannover Sprague-Dawley rats (HnSD) versus (mRen2)27 rats. There were no differences in decay time constants [PTP=9 minutes; LTP=120 to 150 minutes in both (mRen2)27 and HnSD]. However, angiotensin (Ang) II increased PTP and LTP in SCG isolated from (mRen2)27 rats to a greater extent than HnSD. Candesartan (an AT₁ antagonist) blocked the potentiation in both groups. Without a preceding tetanic pulse, 16-nM Ang II induced similar significant increases in ganglionic transmission of 14% in both strains. Assessment of Ang II receptors by ¹²⁵I-[Sar¹Thr⁸]-Ang II binding showed that the AT₁-receptor subtype predominates in the ganglia. The density of receptors in the SCG was comparable in (mRen2)27 and HnSD rats, whether measured in tissue from ganglia removed and frozen versus ganglia used in the transmission testing, suggesting that upregulation of receptors in vitro after removal of SCG did not occur. The divergence of effects of Ang II on LTP and PTP [greater in (mRen2)27 than HnSD] and nontetany ganglionic transmission (similar in both strains) may reflect different locations of receptors (pre- versus postsynaptic) or different signaling mechanisms involved in the two responses. We suggest that functional Ang II receptors in SCG mediate physiological actions of Ang II on ganglionic transmission and may play a pivotal role in hypertension.

Key Words: angiotensin II • rats, transgenic • autonomic nervous system • hypertension • arterial • receptors

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