DOPAMINE-SENSITIVE ADENYLATE-CYCLASE IN PLANARIA DUGESIA-GONOCEPHALA

1. The adenylate cyclase activity present in the particulate fraction of planaria homogenates has been characterized. 2. The enzyme requires divalent cations (Mg2+), and a K(m) for ATP of 0.58 at 30-degrees-C was measured. 3. GTP and Gpp(NH)p, in an optimal range of 10(-4)-10(-5)M, increase the enzymatic activity. 4. In the presence of GTP, dopamine stimulates the adenylate cyclase and its action is inhibited by dopaminergic antagonist. 5. Both D-1 and D-2 selective dopaminergic agonists stimulate the enzymatic activity and their action is selectively antagonized by D-1 and D-2 antagonists. 6. The high concentrations required for some D-1 and D-2 agents to be effective, suggest an only partial consistency with mammalian dopaminergic receptors.