Contractile responses of canine coronary collateral vessels.

This study examines the responses of coronary collateral vessels to various vasoconstrictors and compares them with responses of 3 different divisions of the native coronary arterial trees in dogs. Only high concentrations of phenylephrine induced contractions in collateral vessels and medium coronary arteries, whereas even a high concentration of this agent did not affect small coronary arteries. Lower concentrations of serotonin or ergonovine elicited contractions in collateral vessels, and medium and large coronary arteries, but even a high concentration of these agents did not affect small coronary arteries. Angiotensin II (10(-7) M) elicited prominent contractions in the following order: small vessels, collateral vessels, medium and large coronary arteries. These results indicate that well-developed collateral vessels behave like native medium diameter coronary artery, and that the tonus of collateral vessels is possibly influenced by various vasoactive substances.