Dopamine data preparation

A very intriguing observation noted above was the possibility of presynaptic dopamine agonist activity with SK F 87516 and SK F 85174. The inhibitions of the constrictor response and the 3H -norepinephrine release induced by brief intermittent periarterial sympathetic nerve stimulation of the perfused rabbit ear artery is a convenient in vitro assay for presynaptic dopamine agonist activity (30). In this preparation, both SK F 85174 and SK F 87516 inhibited both stimulation responses with an EC50 of about 100 riM. Another measure of D-2 activity is inhibition of specific spiroperidol binding (20). Comparison of these data (Table I) showed that SK F 85174 is thirty times as potent as dopamine, and thus is a potent D-2 agonist. However, the activity in adenylate cyclase stimulation indicates that this compound may be best described as a D-l/D-2 agonist (19, 20). 

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