In the present study we have identified biochemically DA receptors in rat Lower Esophageal Sphincter (LES) and have identified their role in the control of the sphincter motility. Dopamine (DA) both stimulated and inhibited cyclic AMP formation in rat LES; the pharmacological characterization of these effects indicated that they were mediated by D-1 and D-2 receptors, respectively. The results obtained with LES helical strips showed that DA plays both inhibitory and stimulatory effects on the sphincter function; the pharmacological characterization with selective D-1 and D-2 agonists and antagonists strongly suggested that D-1 receptors are involved in LES contraction, while D-2 receptors mediate the relaxation of the sphincter. The same results were obtained by measuring intraluminal LES pressure in anesthetized rats. The selective D-1 agonist fenoldopam (40 μg/kg, i.v.) increased the LES pressure; on the other hand bromocriptine (10 μg/kg, i.v.), which preferentially interacts with D-2 receptors, induced a decrease of the resting LES pressure.
ASJC Scopus subject areas