Purpose: To investigate the effect of one-bottle dentin bonding systems on pulpal hemorrhage control in direct pulp exposures through contraction of pulp blood vessels using the rat carotid artery model. Materials and Methods: Four dentin bonding agents (Prime & Bond 2.1, Prime & Bond NT, Syntac Single Component and Single Bond) were used. The efficacy of bonding agents were compared to that of epinephrine (control) in the viewpoint of the concentration applied and the contraction forces induced on the smooth muscle were recorded using a force displacement transducer. Results: Three of the test materials produced epinephrine-like contractions on the rat carotid artery (smooth muscle) while no reading could be achieved with Single Bond. A ranking between the bonding agents for contraction forces was obtained as follows: Prime & Bond NT > Prime & Bond 2.1 > Syntac Single Component (P < 0.05).