A series of dopamine analogs was synthesized and assayed for their effect on the dopaminergic D2 receptor. The results are summarized in the following table: % receptor activity when 100 mM dopamine added Compound Ka (nM) % receptor activity Dopamine 1.9 19.0 18.4 1 180 -12.1 -6.2 37 0.1 0.8 3 0.46 19 19 4 14.9 12.2 18.4 a) Compare the affinities of analogs 1-4 to that of dopamine. b) Compare the efficacies of analogs 1-4 to dopamine. c) What type of effect (agonist, antagonist, etc.) is produced by 1-4?