Coronary reflex explained

Coronary reflex is the change of coronary diameter in response to chemical, neurological or mechanical stimulation of the coronary arteries.The coronary reflexes are stimulated differently from the rest of the vascular system.

Causes of coronary constriction

Chemical

• N-nitro L-arginine
• indomethacin
• glibenclamide
• tetraethylammonium chloride
• caffeine

Other

• Cold

Causes of coronary dilation

Cocaine abuse frequently can cause a coronary spasm, resulting in a spontaneous myocardial infarction.

Chemical

• Versed (Midazolam): a coronary dilator. In midazolam's presence, dilation was unaffected by N-nitro L-arginine, indomethacin and glibenclamide.
• Tetraethylammonium chloride, an inhibitor of the BKCa K+ channel (a high conductance Ca2+-sensitive K+ channel), dose dependently attenuated the vasodilating effect of midazolam ^[1]
• Estrogen has been shown to abolish abnormal cold-induced coronary constriction.^[2]

Notes and References

1. N-nitro L-arginine causes coronary vasoconstriction and inhibits endothelium-dependent vasodilatation in anaesthetized greyhounds. O.L. Woodman . G.J. Dusting . Br. J. Pharmacol. . 1991 . 103 . 1407–1410 . 1909199 . 2 . 1908370 . 10.1111/j.1476-5381.1991.tb09802.x.
2. 10.1378/chest.114.6.1556 . Estrogen Acutely Abolishes Abnormal Cold-Induced Coronary Constriction in Men* . Steven E. Reis, MD . Richard Holubkov . Kathleen A. Zell, BSN . AJ. Conrad Smith, MD . Howard A. Cohen, MD . Marc D. Feldman, MD . Roger S. Blumenthal, MD . Chest . 1998 . 114 . 1556–1561 . 9872188 . 6. free .