Short Communication: PDF Onlyα2-Agonist Activity of the Dopamine DA2-Agonist LY171555Cohen, Marlene L.; Shaar, Carl J.; Colbert, Walter E.Author Information Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana Received March 26, 1984; revision accepted July 2, 1984. Address correspondence and reprint requests to Dr. Cohen at Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285. Journal of Cardiovascular Pharmacology: November 1984 - Volume 6 - Issue 6 - p 1245-1248 Free Abstract Summary: LY171555 is the active enantiomer of the racemate LY141865, a selective DA2-receptor agonist. LY171555 (10-7-10-4M) inhibited the twitch response to field stimulation in the adrenergically innervated rat vas deferens, a response due to activation of α2-receptors as evidenced by total blockade with yohimbine (10-6M). The dopamine receptor antagonist sulpiride (10-5M) produced a small shift in the concentration-response curve to LY171555, consistent with the modest α2-antagonist activity of sulpiride. LY171555 (10-10-10-8M) inhibited prolactin release from the anterior pituitary in vitro, a response due to activation of DA2-receptors as indicated by total blockade with sulpiride (10-6M). Thus, in addition to its predominant DA2-agonist activity, LY171555 can activate α2-receptors in concentrations similar to those necessary for activation of histamine H2-receptors. Such concentrations were approximately 2,250-fold higher than necessary for DA2-receptor activation. © Lippincott-Raven Publishers.