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Angiotensin II receptor binding and the baroreflex pathway
A M Allen1, M J McKinley, B J Oldfield
1Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
Summary
Angiotensin II (Ang II) receptors are found in key brain areas of the baroreflex pathway. These receptors may help Ang II control autonomic activity and cardiovascular function.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Autonomic Nervous System Research
Background:
- Angiotensin II (Ang II) is a key hormone influencing central autonomic and cardiovascular regulation.
- Understanding Ang II's central targets is crucial for deciphering autonomic control mechanisms.
Purpose of the Study:
- To map the distribution of Angiotensin II (Ang II) receptors within the baroreflex pathway.
- To investigate the role of these receptors in modulating autonomic and cardiovascular function.
Main Methods:
- In vitro autoradiography to visualize Ang II receptor binding sites.
- Nodose ganglionectomy and vagal ligation to trace receptor transport.
- Microinjection of Ang II into specific brain regions in cats.
Main Results:
- Ang II receptor binding sites were identified in the nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus, ventrolateral medulla, spinal cord, nodose ganglion, and heart.
- Evidence suggests Ang II receptors are synthesized in the nodose ganglion and transported via the vagus nerve.
- Ang II microinjection into the rostral ventrolateral medulla induced a pressor response mediated by sympathetic activity.
Conclusions:
- The baroreflex arc contains multiple regions with Ang II receptors.
- These receptors likely mediate Ang II's effects on cardiovascular control and autonomic function.
- Presynaptic Ang II receptors in the NTS may inhibit neurotransmitter release, contributing to baroreflex inhibition.