A comparison of the responses to some dopamine-receptor agonists and antagonists in the isolated perfused rat kidney.

Bromocriptine (5-100 microgram; 6.7 X 10(-9) - 1.3 X 10(-7) mol.), SK&F 38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine, 0.5-5 mg; 1.7 X 10(-6)-1.7 X 10(-5) mol.) and apomorphine (20-200 microgram; 6.4 X 19(-8)-6.4 X 10(-7) mol.) administered into rat kidneys perfused with physiological solution containing vasopressin and pretreated with an alpha-adrenoreceptor antagonist produced vasodilator responses similar to dopamine (50-100 microgram; 2.6 X 10(-8)-5.3 X 10(-7) mol.). THe responses to bromocriptine, SK&F 38393 and apomorphine were found to be significantly reduced by the dopamine receptor antagonist ergometrine (50 microgram; 1.1 X 10(-7) mol.). Metoclopramide (250 microgram; 7.4 X 10(-7) mol.) was found to be an effective antagonist of dopamine, bromocriptine, SK&F 38393 and apomorphine. Apomorphine (20, 50 microgram; 6.4 X 10(-8), 1.6 X 10(-7) mo.) was found to act as a partial agonist on dopamine receptors in this preparation.