Dopaminergic modulation of human adrenal medulla: indirect evidence for the involvement of DA-2 receptors located on the chromaffin cells.

1. Pharmacological blockade of DA-2 receptors causes a significantly higher epinephrine (E) response to physical exercise in normal man. 2. The present study was undertaken to evaluate whether dopaminergic modulation of E secretion is present also for a stimulus such as glucagon which acts directly on chromaffin cells. 3. Seven normal males were studied in a single blind randomized manner on two separate occasions, after pre-treatment with placebo or domperidone (DMP; 20 mg orally). Plasma E and norepinephrine, plasma prolactin, heart rate and blood pressure were measured on two separate occasions (placebo vs DMP) before and after a glucagon (1 mg i.v.) stimulation test. 4. Glucagon caused an increase in plasma E either after placebo (P = 0.043) or after domperidone (P = 0.012). DMP administration caused a significant increase in plasma E (P = 0.0008). Absolute increase in plasma E after glucagon was significantly higher after DMP than after placebo (P = 0.030). 5. As the dopaminergic modulation of human adrenal medulla is confirmed also for a stimulus acting directly on chromaffin cells, the results of the present study suggest that the DA-2 receptors responsible for the modulation are located on medullary cells.

RCT Entities:   Population Interventions Outcomes