Related Experiment Videos
Heterogeneous response patterns of aortae to norepinephrine
Artery
|January 1, 1980
Summary
Hypertension in rats reduces aortic relaxation mediated by beta-2 adrenergic receptors, particularly in the thoracic aorta. This suggests altered vascular responses in spontaneously hypertensive rats compared to controls.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Hypertension Research
Background:
- Vascular smooth muscle response to adrenergic agonists is critical for blood pressure regulation.
- Spontaneously hypertensive rats (SHR) exhibit altered cardiovascular function compared to normotensive Wistar-Kyoto (WKY) rats.
- Understanding differential aortic responses in hypertension is key to explaining varied clinical observations.
Purpose of the Study:
- To investigate the concentration-dependent contractile and relaxation responses of thoracic aorta (TA) and abdominal aorta (AbA) to adrenergic agonists in SHR and WKY rats.
- To elucidate the role of beta-adrenoreceptors, specifically beta-2, in mediating these vascular responses.
- To determine if early hypertension affects these adrenergic-mediated relaxation mechanisms.
Main Methods:
- Determination of concentration-contractile response curves using adrenergic agonists (epinephrine and norepinephrine) on isolated TA and AbA from SHR and WKY rats.
- Assessment of vascular relaxation at high agonist concentrations.
- Pharmacological blockade with propranolol and stimulation with the beta-2 agonist salbutamol to identify receptor involvement.
Main Results:
- WKY TA showed maximum response to epinephrine (E) and norepinephrine (NE) at specific concentrations, followed by relaxation at higher doses.
- SHR TA exhibited significantly less relaxation compared to WKY TA at higher E and NE concentrations.
- Abdominal aortae (AbA) from both SHR and WKY rats showed no significant relaxation at high E and NE concentrations; relaxation responses were similar between groups.
- Propranolol suggested beta-adrenoreceptor mediation, and salbutamol confirmed a partial beta-2-adrenoreceptor role in relaxation.
- The beta-2 adrenergic relaxation response was diminished in the TA of early hypertensive SHR.
Conclusions:
- High concentrations of epinephrine and norepinephrine induce relaxation in rat aortae, partly mediated by beta-2 adrenoreceptors.
- Early hypertension in SHR is associated with a decreased beta-2 adrenergic relaxation response in the thoracic aorta.
- These differential vascular responses may contribute to the variability in findings regarding vascular sensitivity to vasoactive agents in hypertensive models.