Striatal adenylate cyclase activity stimulation

As much as higher concentrations of dopamine are required to stimulate striatal adenylate cyclase activity as compared to the affinity of the drug for the agonistic sites of the receptor, the sensitivity of the anterior pituitary adenylate cyclase to dopamine agonists in both human prolactinoma (26) and rat adenohypophysial homogenate (31) is lower than the potency of the compounds to inhibit prolactin secretion in intact cells (2). This variable loss of sensitivity upon cell homogeneization is a phenomenon frequently observed in other systems (32). 

An important criteria of D-l dopamine agonist activity is stimulation of dopamine-sensitive adenylate cyclase (8). Table I compares the activity of the four benzazepines and dopamine as stimulants of rat striatal adenylate cyclase. All of the benzazepines are only partial agonists with SK F 82526 and SK F 85174 being about 20 times more potent than dopamine and SK F 38393 and SK F 87516 being similar in potency to dopamine. 

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