Effects of α-adrenergic receptor blockade on coronary circulation in conscious dogs

P. Macho, T. H. Hintze, Stephen Vatner

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The effects of three α-adrenergic-receptor blocking agents (phentolamine, prazosin, and trimazosin) were compared on the coronary circulation and left ventricular (LV) function in chronically instrumented conscious dogs. The three α-adrenergic-receptor blocking agents were administered in equidepressor doses (mean arterial pressure fell by ~20%) and in the presence of β-adrenergic-receptor blockade and constant heart rate. LV systolic pressure, LV end-diastolic pressure, and LV end-diastolic diameter also fell similarly with the three drugs. Phentolamine decreased the time rate of change of LV pressure (LV dP/dt) by 21 ± 3%, whereas trimazosin and prazosin decreased LV dP/dt only by 14 ± 2 and 11 ± 2%, respectively. LV velocity was not changed with trimazosin and prazosin but decreased with phentolamine by 12 ± 4%. The three drugs exerted differential effects on the coronary circulation. Only trimazosin increased coronary blood flow (18 ± 5%). Trimazosin decreased late diastolic coronary resistance (LDCR) by 35 ± 2%, which was significantly more than reductions in LDCR induced by prazosin (22 ± 2%) and by phentolamine (11 ± 3%). A test dose of phenylephrine (5.0 μg/kg) increased mean arterial pressure by 53 ± 3.5 mmHg. After trimazosin, prazosin, and phentolamine, the same dose of phenylephrine increased mean arterial pressure by 24 ± 2.1, 14 ± 1.6, and 1.9 ± 0.6 mmHg, respectively. The response after phentolamine was significantly less than with trimazosin (P < 0.01) and prazosin (P < 0.02). Thus the capacity of these three α-adrenergic-receptor blocking drugs to dilate coronary vessels is inversely proportional to their capability to block exogenous α-adrenergic-receptor agonists.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume12
Issue number1
StatePublished - Jan 1 1982

Fingerprint

Coronary Circulation
Prazosin
Phentolamine
Adrenergic Receptors
Dogs
Arterial Pressure
Adrenergic Antagonists
Phenylephrine
Ventricular Pressure
Pharmaceutical Preparations
Blood Pressure
Adrenergic Agonists
trimazosin
Left Ventricular Function
Coronary Vessels
Heart Rate

All Science Journal Classification (ASJC) codes

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)
  • Physiology

Cite this

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title = "Effects of α-adrenergic receptor blockade on coronary circulation in conscious dogs",
abstract = "The effects of three α-adrenergic-receptor blocking agents (phentolamine, prazosin, and trimazosin) were compared on the coronary circulation and left ventricular (LV) function in chronically instrumented conscious dogs. The three α-adrenergic-receptor blocking agents were administered in equidepressor doses (mean arterial pressure fell by ~20{\%}) and in the presence of β-adrenergic-receptor blockade and constant heart rate. LV systolic pressure, LV end-diastolic pressure, and LV end-diastolic diameter also fell similarly with the three drugs. Phentolamine decreased the time rate of change of LV pressure (LV dP/dt) by 21 ± 3{\%}, whereas trimazosin and prazosin decreased LV dP/dt only by 14 ± 2 and 11 ± 2{\%}, respectively. LV velocity was not changed with trimazosin and prazosin but decreased with phentolamine by 12 ± 4{\%}. The three drugs exerted differential effects on the coronary circulation. Only trimazosin increased coronary blood flow (18 ± 5{\%}). Trimazosin decreased late diastolic coronary resistance (LDCR) by 35 ± 2{\%}, which was significantly more than reductions in LDCR induced by prazosin (22 ± 2{\%}) and by phentolamine (11 ± 3{\%}). A test dose of phenylephrine (5.0 μg/kg) increased mean arterial pressure by 53 ± 3.5 mmHg. After trimazosin, prazosin, and phentolamine, the same dose of phenylephrine increased mean arterial pressure by 24 ± 2.1, 14 ± 1.6, and 1.9 ± 0.6 mmHg, respectively. The response after phentolamine was significantly less than with trimazosin (P < 0.01) and prazosin (P < 0.02). Thus the capacity of these three α-adrenergic-receptor blocking drugs to dilate coronary vessels is inversely proportional to their capability to block exogenous α-adrenergic-receptor agonists.",
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Effects of α-adrenergic receptor blockade on coronary circulation in conscious dogs. / Macho, P.; Hintze, T. H.; Vatner, Stephen.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 12, No. 1, 01.01.1982.

Research output: Contribution to journalArticle

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