Related Experiment Videos
Preoptic recess alpha-adrenoceptors control cardiovascular responses to hyperosmolality
1Department of Physiology and Biophysics, University of Tennessee, Memphis 38163, USA.
The American Journal of Physiology
|April 1, 1997
Summary
Alpha-adrenoceptors in the anteroventral third ventricle (AV3V) regulate cardiovascular responses to hypertonicity. Blocking these receptors in the AV3V, but not the diagonal band of Broca (DBB), altered blood pressure and heart rate.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Autonomic Nervous System
Background:
- Peripheral hypertonicity triggers significant cardiovascular adjustments.
- Alpha-adrenoceptors are implicated in regulating blood pressure and heart rate.
- Specific brain regions like the AV3V and DBB are involved in cardiovascular control.
Purpose of the Study:
- To investigate the role of alpha-adrenoceptors in the AV3V and DBB.
- To determine their involvement in mediating cardiovascular responses to hypertonicity.
- To differentiate the roles of alpha1- and alpha2-adrenoceptor subtypes.
Main Methods:
- Conscious rats were infused with isotonic or hypertonic NaCl.
- Microdialysis was used to perfuse antagonists (phentolamine, yohimbine, prazosin) or agonists (phenylephrine, clonidine) in the AV3V, DBB, or lateral ventricle.
- Mean arterial blood pressure (MAP) and heart rate (HR) were continuously monitored.
Main Results:
- Hypertonic NaCl infusion increased MAP and decreased HR.
- AV3V administration of phentolamine or yohimbine abolished both MAP and HR responses.
- Prazosin in the AV3V selectively blocked the bradycardia; DBB or lateral ventricle perfusions had no effect.
Conclusions:
- Alpha-adrenoceptors within the AV3V are critical for cardiovascular adjustments to hyperosmolality.
- Both alpha1- and alpha2-adrenoceptor subtypes in the AV3V contribute to these responses.
- The DBB does not appear to play a significant role in this specific regulatory pathway.